Big Boo
"Oh man, once you look the other way I'm gonna kill your ass!"
— Big Boo to Mario
Big Boo is an enemy that first appeared in the Ghost Houses of Super Mario World. They are the same as regular Boos, but are larger in size. One Big Boo made an appearance in the popular Bowser's Kingdom show. This Boo is shown to speak in a very deep voice in his appearances.
Bowser's Kingdom[]
Big Boo first appears in Episode 3, where he is seen among the many minions in the World 3 Castle along with The Inaudible Thwomp, Lemmy Koopa, Dry Bones, a Hot Head, and the Karate Duo Number 1. When Mario eventually reaches him, Big Boo says that he's going to get him once Mario stops looking at him. Much to Big Boo's dismay, Mario dodges him by walking backwards while facing him.
In Episode 8, Big Boo appears as the Spooky Speedster after Jeff transforms into a Boo via Boo Mushroom. He tempts Jeff into a race for a star, but Hal says they're not in the mood. Suddenly, Luigi appears and sucks up Big Boo with his Poltergust 3000.
He makes a small cameo in Episode 10, where he is shown scaring Mallow, which the latter is in-between the Karate Duo Number 1.
Big Boo makes a reappearance in the Bowser's Kingdom Movie, where he is seen in the Ghost House that Hal (disguised as Luigi) and Princess Toadstool/Peach visit while searching for Jeff (disguised as Mario). After appearing, Peach becomes scared and tells Hal to kill him, but Hal says to her that ghosts can't be killed. Big Boo later disappears after Petey Piranha breaks in and throws up on Hal and Peach.
In Episode 666, Big Boo is one of the few survivors in the castle on the Doughnut Plains (most likely because he's a ghost). After Geno finishes his story of how the zombie invasion occurred, Big Boo says its because "the devil was upon them", in the form of Ganon. He then says he's only joking and that the rest of the survivors are "all gonna die", before disappearing in a flash.