You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.

Category: WHAT KIND OF ANIMAL MASCOT? 
Clue: Elmer's glue
a bull

Category: SO GREAT THEY NEED 2 NICKNAMES 
Clue: By career's end Wayne Gretzky was "The Great One"; earlier he was this, also a Chaplin film title
"the kid"

Category: WHAT'S THE MATTER...YELLOW?? 
Clue: Call it crazy, but unlike other types of these birds, the yellow-billed one builds its own nest instead of invading

cuckoo