Boo Buddies

Circling Boo Buddies are a formation of many Boos found in Super Mario World. They chase and circle around Mario and Luigi, slowing down their process. Touching any single one of the Boos that make up a Boo circle can prove to be fatal for the Mario Bros.. The only way to get rid of them was to touch them while they are invincible from a Star or by going to another room. Thankfully, they only appear in small rooms in Ghost Houses.

Boo Buddies also make an appearance in New Super Mario Bros. Wii (after an 18-year long absence, not counting remakes), in the World 5 Ghost House, where they act as they did in Super Mario World.

Another similar Boo formation is the Boo Buddy Snake.