From Monkey Island wiki
Wharf Rat™ is an entertainer at the Carnival of the Damned (a.k.a. the Big Whoop Amusement Park) on Monkey Island. His only appearance is in The Curse of Monkey Island, where he runs a booth in which guests can fire pies from a cannon at a mime called Monty Meringue™. He is extremely grouchy, particularly about the bad-smelling costume he has to wear, and really dislikes his co-worker Dinghy Dog™. He smokes a cigar while he works. He doesn't allow Guybrush to play the cannon game but will fire pies at Monty Meringue™ to shut him up. Wharf Rat™'s fate after LeChuck's death and the park's destruction is unknown.