Bartholomew Byfard Boo is a ghost in "Ghost Who's Coming to Dinner", an episode of A Pup Named Scooby-Doo.
Mr. Boo is gentle and friendly to humans. He is also afraid of ghosts, despite being one himself.
Mr. Boo hired the Scooby-Doo Detective Agency to clear his name when BooBeard started causing trouble in his home, so Mr. Boo's house wouldn't be torn down lest he go down with it.
- 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 Pac-Man cartoon.
- Chronologically, Mr. Boo is the first real ghost the gang ever encountered and befriended.
- Daphne Blake doesn't believe him to be a real ghost at first.
- Mr. Boo's mannerisms and voice are similar to Droopy, another character Don Messick and Frank Welker had voiced.