Classic "Arnold" Jokes:
* A tutu: The image of the Terminator in a tutu is hilarious!
* A frilly apron: Contrasting his tough-guy image with a frilly apron is sure to get some laughs.
* A pink bunny suit: This is pure comedy gold.
* A tiny, sequined dress: The juxtaposition of his physique with a tiny dress would be incredibly funny.
More General Funnies:
* A giant, fluffy bathrobe: The image of him trying to navigate a fluffy bathrobe is funny in itself.
* A pair of bright pink Crocs: This is a classic example of an item that is universally considered "uncool" - perfect for a comedic effect.
* A pair of granny panties: This is a surefire way to break the "Terminator" image.
* A giant, inflatable T-Rex costume: The contrast of his tough-guy persona with a goofy dinosaur costume is ripe for comedy.
Bonus:
* A tiny, adorable puppy outfit: Picture him in a little puppy costume with a wagging tail. It's too cute to resist!
Remember, the key is to choose something that plays with his image and is unexpected.