Showa The original Mechagodzilla was created as a weapon of destruction by the Simians.
It first appeared in a pseudo-flesh outer covering, masquerading as the real Godzilla during attacks against Japan in Godzilla vs. Mechagodzilla. Curiously, while the Simians gave Mechagodzilla a laser beam in its mouth to mimic Godzilla's atomic breath, they didn't bother replicating Godzilla's unique roar. Godzilla's ally Anguirus wasn't fooled by the impostor, but in the resulting fight Mechagodzilla broke Anguirus' jaw and sent him fleeing underground. Although the battle went badly for Anguirus, it tipped humanity off to the charade due to the fact that while Godzilla and Anguirus had initially been enemies in 1955 in the second Godzilla film, they had been firm allies ever since, and the two were known to come to one another's aid in combat against other monsters. Anguirus attacking 'Godzilla' was seen as a complete shock. Anguirus had also exposed a piece of MechaGodzilla's true mechanical nature by ripping off a piece of the disguise the machine was covered in, though most humans didn't seem to notice it.
Soon the true Godzilla appeared and exposed his foe's metallic form completely. Interestingly, after losing its disguise, Mechagodzilla's fingers lost all mobility and it lost the beam in its mouth (No explanation for this was ever given). The battle resulted in a tie, however, and in the end it took the combined might of Godzilla and King Caesar to remove Mechagodzilla's head from his shoulders, ending the threat.
The Simians rebuilt their dreadnought for another try in Terror of Mechagodzilla one year later. Having learned the value of teamwork firsthand, the Simians called in an old debt to pair Mechagodzilla with the aquatic dinosaur Titanosaurus that had been discovered by a Dr. Mafune.
This time there were some modifications made, mainly turning the mecha into a true cyborg by giving it living human brain cells. This was accomplished by integrating its control circuitry into the body of Dr. Mafune's daughter Katsura, as well as a variety of other cybernetic enhancements. Also Mechagodzilla's main control system was moved down into its neck so it could function unimpaired if Godzilla again attempted to decapitate it. Godzilla's perseverance combined with the timely self-sacrifice of Mechagodzilla's operator (Katsura killed herself) brought the machine down for good. The King of the Monsters buried Mechagodzilla's shattered form deep underground to prevent another repair job.
The original Mechagodzilla is the only one to be referred to by numerics within the movies themselves. When it is rebuilt in its second appearance, the "MG" emblazoned on its arm has a "2" added to it. It is still usually referred to as simply "Mechagodzilla" by the characters.
Mechagodzilla in Terror of MechagodzillaThis version of Mechagodzilla was rated Number 15 of the 50 Best Movie Robots by The Times, beating other such legends as C-3PO from Star Wars, the T-1000 from Terminator 2: Judgement Day, and Optimus Prime from Transformers.
 Arsenal The Showa Mechagodzilla has armour constructed out of a mysterious and nearly indestructible alloy known as "Space Titanium." It is also equipped with a staggering amount of firepower.
Mechagodzilla is capable of firing a rainbow colored optical beam that was able to match Godzilla's atomic breath, known as the "Space Beam". Its head can rotate a full 360 degrees, allowing the robot to shoot down an opponent that might attempt to approach from behind. Mechagodzilla's head is also able to generate a cylindrical force-field around the robot's body by spinning around rapidly. When disguised as Godzilla, Mechagodzilla used a Flamethrower from its mouth to mimic the real Godzilla's atomic breath. After the disguise was destroyed, Mechagodzilla never used that weapon again.
The Showa Mechagodzilla is also equipped with powerful missiles in its fingers, knees, and even its toes. These missiles can explode on contact with a target or lodge in an enemy's flesh like darts. Located under a hatch in Mechagodzilla's chest is a weapon that fires a jagged orange energy beam with enough power to cut a mountain in half. Mechagodzilla 2 was able to increase the velocity of its finger missiles by rapidly rotating its hands and could also fire a ray from under its head when it was ripped off.
Mechagodzilla is shown to be capable of using its beam and missile weapons simultaneously and against multiple targets, at one time engaging Godzilla to the front and King Caesar to the rear.
 Video game appearances The Shōwa Mechagodzilla appears in the video games Godzilla: Monster of Monsters for the Nintendo Entertainment System, Godzilla for the Game Boy, The American version of Super Godzilla for the Super Nintendo, Godzilla Battle Legends for TTI Duo, Godzilla Generations for the Dreamcast and Godzilla Generations: Maximum Impact for the Dreamcast. He appears in the Wii version of Godzilla: Unleashed, making it the first game with all three Mechagodzillas. He is part of the Alien faction, being a rebuilt version of one of the Vortaak's original weapons in conquering the Earth.
 Heisei The Heisei Mechagodzilla, from Godzilla vs. Mechagodzilla II, was created by the United Nations Godzilla Countermeasures Center using Futurian technology scavenged from the remains of Mecha-King Ghidorah. When Godzilla attacked the city of Kyoto, Mechagodzilla was deployed against him. The mechanical kaiju acquitted itself well, but was eventually defeated due to a voltage backsurge during their electrocution of Godzilla. One of the back-up pilots, Kazuma Aoki, suggested merging Mechagodzilla with the Garuda, a smaller airship that had been constructed by the UNGCC before Mecha-King Ghidorah's remains had been salvaged.
Super-MechagodzillaKazuma, in fact the chief designer and main pilot of Garuda to start with, found some personal redemption as his idea is approved. The combined form of the two mechs, dubbed Super-Mechagodzilla, is unleashed against the King of the Monsters and Fire Rodan. In the heat of battle, Kazuma personally detaches Garuda and flies against Fire Rodan while the other Mechagodzilla crew continue against Godzilla. Kazuma is defeated, but manages to reattach the Garuda to Mechagodzilla to form Super-Mechagodzilla.
Super-Mechagodzilla proceeds to destroy Godzilla's secondary brain killing Godzilla and then moves in to destroy Godzilla's body. Fire Rodan leaps to Godzilla's defense, but is killed by a blast from Super-Mechagodzilla's Megabuster Ray. Upon dying, Fire Rodan's body dissolves, releasing the radioactive energy within its body and reviving Godzilla. As Fire Rodan dissolved, he filled the air with a superheated, radioactive dust, which melted Super-Mechgodzilla's diamond coating. As a result, Super-Mechagodzilla was rendered defenseless against the revived monster. Godzilla, temporarily supercharged with radiation, destroys the mech with his red spiral atomic breath as revenge for Rodan's death. Super-Mechagodzilla's crew escape uninjured.
 Arsenal The Heisei Mechagodzilla has an impressive and varied arsenal built only to destroy Godzilla and other monsters, which makes it a powerful adversary. Mechagodzilla is protected by an armor plating made from an alloy called NT-1, which is coated in a layer of artificial diamond that allows it to absorb energy from Godzilla's atomic breath and transfer it to its ultimate weapon, the plasma grenade, located on its abdomen. Mechagodzilla was also able to absorb energy from Fire Rodan's Uranium heat ray. This weapon could be rendered useless if the plasma pool used to channel the energy overheated, this diamond coating is the only real reason Mechagodzilla survived any of its encounters with Godzilla. Mechagodzilla also possesses laser cannons in its eyes and a mega buster in its mouth with destructive power equitable to Godzilla's atomic breath. It can fire tranquilizer missiles from its hips, paralysis missiles from the shoulders, and shock anchor cables from its wrists which deliver a powerful electrical surge into its opponent. After Godzilla used his nuclear reverse to send a back surge through the cables and into Mechagodzilla, the shock cables were upgraded into a more powerful version called the G-Crusher which was used to destroy a secondary brain in Godzilla's lower spine.
Finally, Mechagodzilla can attach to the airship Garuda and becomes Super-Mechagodzilla. It gains Garuda's powerful maser cannons as well as added thrust from Garuda's jets.
MechaGodzilla 2 is a well known incarnation of Mechagodzilla because it was the only monster to actually kill Godzilla.
 Video game appearances The Heisei Mechagodzilla appeared in the video games Super Godzilla and Godzilla: Monster War for the Super Nintendo, Godzilla: Domination! for Game Boy Advance, Godzilla: Save the Earth for Xbox and PlayStation 2, Godzilla: Destroy All Monsters Melee for Xbox and the Nintendo GameCube, and the Wii and PlayStation 2 versions of Godzilla: Unleashed. Because of his role in Godzilla vs. Mechagodzilla II, he is part of the Global Defense Force faction. He can be bought for 15,000 store points. He has the same moveset as the other Mechagodzillas, aside from a couple techniques. In Save The Earth, his rage attack is MechaGodzilla Cannon. When it does this, it blasts its opponent with its eye lasers, missiles, and Plasma Grenade several times.
In Godzilla: Destroy All Monsters Melee, Mechagodzilla was a somewhat slow moving character who could use powerful lasers and missiles. He could also hover by utilizing the jets on its back.
Heisei Mechagodzilla was removed from the English version of Super Godzilla in favor for the more-known Showa Mechagodzilla. This was due to the fact that at the time of the game's release, Godzilla vs. Mechagodzilla II had not been released on American stores.
Mechagodzilla from Godzilla: Tokyo SOSThe Millennium Mechagodzilla was featured in two films: Godzilla Against Mechagodzilla and Godzilla: Tokyo SOS.
In the Millennium version the original Godzilla had been killed in 1954 by the Oxygen Destroyer, Japan still found itself under attack from other monsters such as Mothra and Gaira over the decades. When a second Godzilla appeared in 1999, this was the last straw. Japan proposed a shocking plan: to dredge up the skeleton of the first Godzilla from Tokyo Bay and use it as a skeleton/framework for constructing a Mechagodzilla, also known as Kiryu or Mecha-G. Yet they were unaware that this bold move would only infuriate and provoke this new Godzilla.
Cloned DNA from the bones was also inserted into the quasi-organic control computers, intended to take over subconscious motor control functions for the crew. By 2002, the metal monster was ready. Mechagodzilla was unleashed, but the cyborg's latent memories were reawakened by the new Godzilla's own roars. Mechagodzilla broke free of its pilot, Akane Yashiro, and proceeded to trash the city (manual overrides being ignored) without the new Godzilla's help for a couple of hours until it ran out of power.
The Japanese public was not amused. Hastily recalled, Mechagodzilla received quite a few weapon upgrades in addition to new computer control software routines. When the new Godzilla attacked again a few days later, both branches of the JSDF tried stopping him without the steel monster's help, but it was useless. With Akane at the ROV controls again, Kiryu was sent out.
The second battle went well until Mechagodzilla's receiver was damaged. Akane wanted to enter Kiryu and affect repairs personally, despite being ordered not to. She then piloted the cyborg directly from its skull, carrying Godzilla out into the bay once more. Akane tried to destroy Godzilla with Mechagodzilla's ultimate weapon, the Absolute Zero Cannon, but the fight ended in a draw. Godzilla went back to the sea (though not before suffering a horribly shredded chest) and Mechagodzilla went back to the body shop after suffering a destroyed right arm, heavily damaged Absolute Zero system, and empty power cells. One year later, Akane sent to America for further flight training. Taking her place in case Godzilla appeared was Akiba, but Mechagodzilla's engineer Yoshito Chujo is the human focus of the film.
Mothra's twin fairies, the Shobijin, appear to warn Japan. They claim that building Mechagodzilla using the real bones was a violation of the natural order of things, sure to keep attracting Godzilla. The twins also claimed that Mothra would gladly take Mechagodzilla's place in protecting Japan if they agreed to dismantle the mechanical beast. Since Mechagodzilla had been built partially to defend against a second attack from Mothra herself, the Japanese declined at first.
But when Godzilla did appear and killed Kamoebas, Mothra voluntarily (but at the same time, reluctantly) engaged him, and Prime Minister Hayato Igarishi was shamed into aiding her. Mechagodzilla flew into battle again. Despite this, the current adult Mothra was killed and Mechagodzilla's transmitter damaged once again. Just like Akane before him, Yoshito entered Mechagodzilla for repairs, but remained inside the mech during the battle after Godzilla's atomic breath had accidentally struck both of the hatch doors damaging and jamming it.
Teaming up with the newly-hatched twin Mothra larvae, Mechagodzilla was able to use his drill in his right arm and injured Godzilla's chest even more, eventually reaching, and tearing up his insides, causing Godzilla to bleed. While Godzilla screamed in pain, Mechagodzilla fired his Triple Hyper Maser at Godzilla, making Godzilla roar to show Kiryu his flash back to Yoshito. Godzilla was then wrapped up by the twin Mothra larvae web. Unable to fight, Godzilla dropped to the ground, making Mechagodzilla almost make a draw in the battle. Mechagodzilla broke free of Akiba's control. Instead of finishing his battle, he merely subdued him, carrying Godzilla out to sea. After releasing Yoshito to safety, Kiryu plunged into the depths with his counterpart and was never seen again. This is the second and final time Mechagodzilla succeeded in killing Godzilla.
 Arsenal Millennium Mechagodzilla is considerably sleeker than other versions of Mechagodzilla, and bears a closer resemblance to Godzilla than the previous versions. While Showa and Heisei Mechagodzilla are constructed of fictional alloys, it is never specified what Kiryu's armor is made out of. It is the first Mechagodzilla to include organic parts, built from the skeleton of the original Godzilla and using Godzilla DNA in its computer system. Additionally, unlike previous Mechagodzillas, this one's tail was able to move which allowed him to use it as a weapon.
Millennium Mechagodzilla is a well balanced machine, and the most agile Mechagodzilla to date, moving with a fluid, almost organic grace. Its armament includes an oral maser cannon, dual laser cannons on each arm, and a flight pack that contains two forward firing rocket launchers and four batteries along its back and sides for launching guided missiles. Upon emptying its payload, the flight pack can detach from his body and launched to push the enemy a safe distance back before being remotely detonated. In Tokyo SOS, the flight pack was modified so that only the weapons pods were fired; leaving the thrusters attached and allowing Mechagodzilla to maintain its aerial capabilities. For close combat, a short blade can be extended from Mechagodzilla's dual laser cannons which was not only able to penetrate Godzilla's nearly impervious hide, but was also able to discharge a crippling electrical surge into his opponent's body. Also in Tokyo SOS, Mechagodzilla's arsenal was upgraded to allow its right hand to collapse into a revolving drill. Like the previous Mechagodzillas, this one was also able to fly; although its limited energy reserves required the machine to be airlifted to the battlefield by two carrier craft.
Millennium Mechagodzilla's most devastating weapon is the Absolute Zero Cannon (a weapon also utilized by the Gotengo). Stored in its chest behind a trio of folding panels, the Absolute Zero Cannon fires a ball of energy that flash froze its target, thereby causing it to disintergrate under the weight of its own mass. After being heavily damaged in Godzilla against Mechagodzilla, the Absolute Zero Cannon was deemed too expensive to repair and was replaced by a Triple Hyper Maser Cannon in Tokyo SOS.
Notes The original MechaGodzilla of the Showa era films is referred to as a cyborg despite the fact that it has no organic components whatsoever, though it does behave like a living being after it is repaired following its initial encounter with Godzilla, as the simian commander gives MechaGodzilla commands via a radio transmitter, and MechaGodzilla then acts on those orders as it sees fit. In its second appearance, it was upgraded to use a human brain (Katsura Mafune) as part of its control circuitry, thus making it a true cyborg in its second and final appearance.
The second MechaGodzilla was simply a machine piloted by a human crew and did not perform any autonomous actions of its own, save for roaring occasionally. Because this MechaGodzila was solely intended as a mecha with the purpose of destroying Godzilla (and presumably any other Kaiju that might have reared its head such as Fire Rodan), no explanation is given for why the robot was able to produce a vocalized roar.
The third MechaGodzilla, Kiryu, is the first genuine cyborg MechaGodzilla, as it is a combination of high technology and DNA cloned from the bones of the first Godzilla. This creature, like the 1954 original, could act on its own, and was capable of breaking free from the controls of the humans responsible for its existence. Unlike the original Godzilla however, this creature was benign towards humans and made a point to communicate, via computer screen, with Yoshito at the climax of Tokyo S.O.S. indicating that it understood human language and may or may not have been listening to every word said in its presence up until it chose to take the modern Godzilla out to sea and to bury itself underwater. Kiryu produced both a mechanical roar and, in a manner still unknown, the roar of a living Godzilla, despite lacking its original organic vocal cords. Presumably, the vocalization device inside Kiryu was not constructed to duplicate the roar of the Godzillas, and so this is an aspect of the creature that remains a mystery.