Metalhead (Teenage Mutant Ninja Turtles)
Metalhead is the name of two different robots in the Teenage Mutant Ninja Turtles franchise. It also refers to a completely different character(albeit spelled separately as "Metal Head"), who is a superhero with manipulative metal hair and a member of the Justice Force from the Mirage comics and 2003 series.
"Metal Head" originally began as a superhero with the power to control his fluid metal hair like tentacles, as well as a member of the Justice Force from the Mirage comics(which later serves a basis for the 2003 incarnation as well).
In the 1987 cartoon series, a separate character named "Metalhead", a robotic turtle, was created by Krang, which would later served as a basis for the 2012 character of the same name but with a different backstory.
In the Mirage Studios' TMNT comic Dome Doom, he is currently retired from super-hero business and lives in Northampton, Massachusetts. In volume 4 issue #6 Shadow's boyfriend, Jay, decides to investigate the farmhouse where she lives in order to get a look at her mysterious grandfather. The boy takes a rifle with him to utilize its scope to get a closer look, and he's discovered by a very unhappy Metal Head.
In the 1987 series, Metalhead first appeared in the episode "The Making of Metalhead" where it was imbued with the thoughts and memories of the Ninja Turtles. This gave Metalhead an identity disorder until Donatello reprograms him to work for the Ninja Turtles. In this appearance, Metalhead replicated the voices of the Ninja Turtles, Shredder, and April O'Neil, meaning that Metalhead was voiced by Cam Clarke, Barry Gordon, Rob Paulsen, Townsend Coleman, Dorian Harewood (who was filling in for James Avery at the time), and Renae Jacobs. He was only seen again when Donatello tries to get him to vacuum their TV room in the episode "Big Bug Blunder".
In the 2003 series, he was a member of the original Justice Force and remains a member of the current Justice Force, making him the only member to serve in both incarnations of the team. Neither incarnation seems to have aged in the intervening decades; in the case of the first incarnation, it was stated that this was due to his artificial nature. Metal Head was also part of the final attack on the Tengu Shredder. Metal Head appears in the "Fast Forward" season episode The Journal. Metal Head also appears in TMNT: Back to the Sewer. He shows up in the episodes "Super Power Struggle" and "Wedding Bells and Bytes".
In the 2012 Teenage Mutant Ninja Turtles series, Metalhead was created by Donatello from a salvaged Kraang droid as a way to upgrade "his" weapons. Donatello could control Metalhead via a NES-like controller while observing the situation through a TV monitor since there are cameras in Metalhead's eyes. Also, Donatello can speak through Metalhead. While Metalhead proved to be nearly unstoppable in combat situations, he was far too clunky and heavy to properly sneak around. Thus, this left Metalhead to be forced to sit out a mission against the Kraang. When his brothers became overwhelmed, Donatello sent Metalhead in. He easily defeated the Kraang attacking them, knocking off the control antenna in the process. One Kraang realized that Metalhead was made from their technology and detached from its robot body where it opted to control Metalhead. With the signal lost without the control antenna, Donatello could not defend Metalhead from the Kraang's control. The Kraang-controlled Metalhead attacked the Ninja Turtles, nearly killing them until Donatello showed up in person. Donatello managed to defeat Metalhead by crashing a support pillar on it. The Kraang controlling it ran off. In "Showdown" Pt. 1, Metalhead was rebuilt by Donatello where it aided the Ninja Turtles in the battle against the Kraang. Apparently now programmed with some degree of independence and operating without any sign of a direct controller, Metalhead drove the Shellraiser into the TCRI building lobby and subsequently attacked the Kraang guards while the Ninja Turtles used their new gliders to infiltrate the building from the roof.
Metalhead appears in Teenage Mutant Ninja Turtles: Turtles in Time as the boss of the second level Alleycat Blues. He has extending punch and kick attacks, as well as a machine gun in his chest.
This version was slightly redesigned for the remake, Turtles in Time Re-Shelled; this version of Metalhead was voiced by Wayne Grayson. The instruction manual of the Super NES version of Turtles in Time erroneously refers to Metalhead as Mechaturtle.
Metalhead appeared as part of both the 1989 and 2012 toy line.