Noun
(idiomatic) The boss, the leader.
Only the top banana can make a decision of that magnitude.
Synonyms: big cheese; see also Thesaurus:important person
(idiomatic, dated) The principal comedian in a vaudeville or burlesque show.
He was hilarious, and remained the top banana on the tour for years.
Antonym: second banana
Leave it to me: I'm always top banana in the shock department. Truman Capote