From the Super Mario Wiki
Fishin' Boos are the ghosts of Fishin' Lakitu found in Super Mario World and Super Princess Peach. They carry a fishing rod and ride a Lakitu's Cloud, much like the living variety. However, instead of a 1-Up Mushroom, Fishin' Boos carry a blue flame and follow the player in a way that makes it hard for them to Jump. Their clouds also do not have faces. A Fishin' Boo has the same immunities as a normal Boo and therefore cannot be jumped on.
Fishin' Boos also make an appearance in Super Princess Peach as Fishing Boos, and a calmer variety called C. Fishing Boo also appears. Both types reside in Shriek Mansion on Vibe Island, and only Rage can defeat them.
Names in other languages