Ultimate Chimera

The Ultimate Chimera (Japanese:  Ultimate Chimera) is a giant, pink Chimera of no defined species, with a small bird on its head, first found in the Chimera Laboratory and later residing in the Empire Pork Building. It is found in Mother 3 and Super Smash Bros. Brawl.

In Mother 3
In this game, it was part of the Chimera project. The Ultimate Chimera was created by Dr. Andonuts in the Chimera Laboratory to be the ultimate killing machine, but it went rogue before he could destroy its last weakness, an off-button on its back. Due to Salsa letting it out of its cage, however, it escaped from the labs. Contact with the Ultimate Chimera is fatal and an automatic game over. It cannot be battled, and because of this, it has no real stats. Its only weakness is that it is battery powered, and has an on/off switch on its back, however, there is no way of pressing this button as Lucas.

In the Chimera Laboratory, it stalks the narrow hallways and small rooms, and there is no way to tell which room it is currently in. There is a split second chance to run away if it spots the party, however. When it spots Lucas, a yellow exclamation mark appears atop its head and a high pitched ping sounds, charging at him at a fast speed. When it changes rooms, a loud clang is heard as it moves, which is a helpful sign for Lucas if he is trapped in a room.

In the Empire Porky Building, however, the Chimera is in one of the bathrooms in the bathroom maze. If Lucas knocks on the door, he'll hear the familiar "Ping!". If he knocks again, he charges the door repeatedly, breaking the lock and granting him access. In this room, a single present is inside, although Lucas has only a brief moment to run back into the hallway, and lure the Ultimate Chimera out of the room to obtain the present.

A white board in the Chimera Laboratory states that if the Chimera escapes, they are to seal all entrances and exits immediately. In addition to this, if the Chimera is to escape outside, they are to feign ignorance. The protocol for if it is seen by civilians had been erased, however.

In Super Smash Bros. Brawl
SmashWiki has an article on the Ultimate Chimera.

It randomly appears on the New Pork City stage. If any fighter is unfortunate enough to get in its path, they get hit with 200% if bitten and 300% damage if the person gets trapped inside it and is sent flying, almost always resulting in a KO. It is possible to temporarily defeat the Ultimate Chimera by smashing the breakable platform at the bottom of the stage while it is standing on it, however. If the player succeeds, it lets out a roar as it falls to its death. It will, however, still re-spawn later. The off button on its back is non-functioning.

Super Smash Bros. for Wii U

 * ''If you ever find yourself faced with this thing, run! There isn't enough time to stop and wonder what two creatures were combined to make this! It's so insanely out of control, even the people at the Chimera Laboratory wish they'd never made it. Eek!