The Ultimate Chimera is something that was created for Porky by the reconstructed Dr. Andonuts. It is invincible, and if you run into it, you will die. There are many versions of Chimeras, but the Ultimate Chimera is easily the strongest. Lucas runs into it at the Chimera Labs looking for Salsa and Samba, who seemed to have released it. When Lucas cornered them the Ultimate Chimera appears and Lucas and Boney's Pigmasks fall off. Salsa then recognizes them for the first time. When the Ultimate Chimera corners them, Salsa comes at the last minute to push the button. The Ultimate chimera collapses and the four escapes the labs. After the group leaves, the bird on top of the Chimera's head activates the Chimera again.
The Chimera seems to be mechanic, has it has a button on it's back that will deactivate it. Pushing the button is the only way to stop it. But it still won't be finished: the little bird on it's head will just reactivate it.
 Super Smash Bros. Brawl
The Ultimate Chimera also appeared in Super Smash Bros. Brawl, in the New Pork City level. Much like in Mother 3, if you touch it, it is instant death. Unless you destroy the wooden floor at the right time, it can't be defeated until it disappears on its own.