Sorry if I gave the wrong Boo before (the Funky Phantom did have a ghost cat named Boo). Are you looking for…
Sully, from Monsters Inc? (If so, yay! If not, sorry again!)
Dr. Dawson
Basil of Baker Street, the Great Mouse Detective
Barney Fife
Andy Taylor
Dave, Stuart, Jerry, Kevin, Mark, Phil, Carl and Josh
Gru
Karen
Matt Murdock
Judge Anderson
Judge Dredd
Cecil
Beany
Augie Doggie
Doggie Daddy
Molly
Fibber McGee
Boo (because the previous two responses, while perfectly valid, still weren’t the one I was thinking of).
Okay, I need a hint.
Tarot, Witch of the Black Rose
Nick Nack
Francisco Scaramanga
Mark Gordon
Jonathan`Smith
Rupert Stilinski
Scott “Teen Wolf” Howard
Pete & Delmar
Ulysses Everett McGill
Bat Cow
Robin
Bolly Quinn, Carli Quinn, Coach, Hanuquinn, Harlem Harley, Harley Queens and Harvey Quinn
Dr. Harleen Frances Quinzel
Vincent D’Agosta
Agent Aloysius Xingu Leng Pendergast
Speaker-to-Animals
Nessus, then Wu
Wong
The Ancient One, then Dr. Strange
Wing