Second Banana is a term that has been around a really long time that meant "second billing" in an acting company. It's most often applied to comedians or comedies now; in such cases it's the supporting comedian, who may also be the Straight Man. The Second Banana may no longer actually get second billing. In terms of characters, it is most often the sidekick, best friend, or co-worker of the protagonist.
- Luigi from the Super Mario Bros. games. Brawl in the Family got a joke out it.
- Art Carney was Second Banana to Jackie Gleason in The Honeymooners.
- In The Andy Griffith Show, and later in Mayberry RFD, Don Knotts was the second banana.
- Neil Patrick Harris's Barney Stinson is the second banana on How I Met Your Mother.
- Vivian Vance was usually Lucille Ball's second banana in I Love Lucy and The Lucy Desi Comedy Hour.
- There was a character (a mouse) actually named Second Banana in some Warner Brothers cartoons, and in some Gold Key comics based on them. He was the sidekick of Merlin the Magic Mouse, a vaudeville-style stage magician.