From the Super Mario Wiki
Mad Big Boos are enemies in Super Princess Peach and can be found in the Shriek Mansion level. Mad Big Boos act the opposite of normal Big Boos; when Peach is not looking at one, it will stop moving, and when she looks at it, it will quickly move towards her, which can be confusing. Despite being mad, the Mad Big Boo has no frown. This suggests that the "Mad" in its name means insane or crazy. It somewhat looks like a miniature Boolossus from Luigi's Mansion.
One of the levels in Shriek Mansion has a Big Boo and Mad Big Boo, and they make a good combination. When Peach looks away, the Big Boo chases her, but when she looks at it, the Mad Big Boo will chase her.
Like other Big Boos, they cannot be defeated by Rage.
Names in other languages
||Boo Atomique Enragé