Because you like Gomez Addams in The Addams Family
Peter Venkman's "research" projects are designed to get undergraduate students to sleep with him. Though it turns out he can bust ghosts. See them in Ghostbusters.
A karate master/rocket scientist/squirrel, Sandy Cheeks is the only one who can clean up the other resident's messes in Bikini Bottom. See them in SpongeBob SquarePants.
Milo Thatch is an enthusiastic researcher without cynicism. See them in Atlantis: The Lost Empire.
Mother Gothel is a great mother as long as you never, ever, break the rules. See them in Tangled.
Alfredo Linguini can whip up five star meals effortlessly. Just don't look under his hat. See them in Ratatouille.
A stylish agent, Agent J would rather improvise than play by the rules. See them in Men in Black.
Frederick Frankenstein is an eccentric (O.K., maybe a little insane) professor who is excited to be delving into his family's past. See them in Young Frankenstein.
Jacob Kowalski is just a baker caught up in an otherworldly adventure. See them in Fantastic Beasts and Where To Find Them.
Chuckie Finster is a baby afraid of everything from clowns to closets, unless his best friend's by his side. See them in Rugrats.