Brobot

Brobot is a Gigantic Robot in Super Paper Mario. He is created to be shaped like Luigi's head. After Luigi loses to Mario and his team in combat, Luigi summons his giant robotic brother and fights Mario's team. Once he loses, Luigi vows to face mario again. He has kept his promise, for he comes back in Chapter 6-1, after Sammer's Kingdom gets destroyed by the Void. His new improved Brobot has arms and legs this time and is more powerful, able to swallow Mario and fire rocket punches at him.

Trivia

 * Brobot's name is a portmanteau of "bro" (a shortened word for "brother" commonly heard in several Mario games) and "robot".
 * Interestingly, the name "Brobot" was previously applied to a recurring character on the television program The Adventures of Jimmy Neutron: Boy Genius, although the two characters' names are likely coincidental; the aforementioned portmanteau isn't so creative.