Bartholomew Byfard Boo, or Mr. Boo as he prefers, is a real ghost.
He is a transparent ghost with a large red nose and wears a small derby hat.
He is extremely friendly and gentle. Also, despite being one he is frightened of ghosts.
A Pup Named Scooby-Doo
Thanks a million, kids. (sniffles) Why, if it wasn't for good friends like you, I'd be—
- When Scooby-Doo sneezes, causing Mr. Boo to lose his sheet, he gets another from the closet. This seems to be a reference to the Ghost Monsters of the PacMan cartoon.
- Chronologically, Mr. Boo is the first real ghost the gang ever encountered and befriended.
- Daphne doesn't believe him to be a real ghost.
- His mannerisms are similar to Droopy Dog, another character Don Messick and Frank Welker had voiced.