Little Mac

Little Mac is a human boxer from the Punch-Out!! series, he has had several encounters with Mario and other characters from the Mario series. He first appeared in the NES title in the Punch-Out!! series.

Punch-Out!!
In Little Mac's first appearance on a home console, as he faught through many tough foes, Mario stood and watched for fair play as the referee.

WarioWare: Smooth Moves
WarioWare: Smooth Moves features a microgame named "Punch-Out!!" based on the game of the same name. There the player in the role of Mario has to count out the boxers knocked down by Little Mac. When successful, Mac cheers his victory.

Super Smash Bros. Brawl
Along with many other Nintendo characters who didn't have many appearances, Little Mac returned in Super Smash Bros. Brawl, here he was an Assist Trophy who would emerge and punch many times at the enemies of whoever released him, until he delivered one final blow that would nearly always KO them.

Captain Rainbow
In Captain Rainbow it is revealed that by the events of this game, Little Mac had been out of work for some time and had become largly obese. It was up to the game's protoganist Nick to help him get back into shape.