Watch for the holes in the ground you can fall through in the last mirror maze. Save option, and use your Pipboy light to navigate better, and you'll eventually make it through this area if you stick to it. Now you'll have to go search the fun house, which is probably one of the most annoying places in the whole park. You won't kill him here though, he'll be back later. It's not too hard of a fight, you'll just have to deal with him performing a disappearing act and healing himself from time to time.
This is in the King Kola castle area, and when you come in here you'll run into a bit of a brawl with a few ghouls, including Oswald the Magnificent. All New Armor & Apparel Locations Guide Location: Kiddie Kingdom King Colas Castle Dropped or rewarded at the end of A Magical Kingdom. Find the scene of Oswald and a ghoul and move on to the theater. You'll have to search the tunnels, the funhouse, and the theater during this quest chain, the tunnels are an easy start as you won't encounter too much of a problem there, and there isn't much interesting happening in them to go exploring around them.
