Mechanical Monsters

Mechanical Monsters are a fleet of Robots created by a Mad Scientist to be used as unstoppable perpetrators of crimes. The robots are gigantic, towering at at least 30 feet. No conventional weapons could stop them, as they were well-armored and quite powerful. They even proved to be a challenge for Superman himself.

Fleischer cartoons
They were stored in the Mad Scientist's base, from which they were remotely controlled. When it came time for them to attack, they converted their arms to wings and flew to their destination. (Fleischer Cartoon: "The Mechanical Monsters")

One of these robots was stored, de-powered, in Superman's Fortress of Solitude in at least two alternate realities, along with many other souvenirs of Superman's previous adventures. ("Superman: Doomsday", Batman: The Brave and the Bold: "The Battle of the Superheroes!")


 * The robots first appeared in the animated short The Mechanical Monsters, which was the second such Superman short.

An army of the Mechanical Monsters appeared again and attacked Metropolis, and Superman flew down from above the Daily Planet and smashed through one. ("Superman 75th Anniversary")

New 52 continuity
Superman battled and defeated an army of Fleischer robots, and then donated these to be studied. They were kept at a facility called "Warehouse 12", until a Superman imposter came and destroyed them. (Superman: "What Price Tomorrow?")
 * This two-minute short showcases many different scenes from different versions of Superman throughout his history, including the Fleischer cartoons era.

Trivia

 * A variation on the Mechanical Monsters appear in the movie Sky Captain and the World of Tomorrow.
 * Another robot based on the Mechanical Monsters appears in the anime film Castle in the Sky.