Decorate the cage and Photoshop a wizards hat and beard on the ham
I don't mind dogs dressed up, so long as they're not looking completely miserable but most other animals don't seem to really know what's happening. I've never seen a happy cat in fancy dress lol
Hams are nervous wee creatures at the best of times and in my experience don't like being restrained for too long. Trying to get anything more complicated than a hat on them is probably going to be annoying or scary for them and maybe quite bitey and bloody for you. If you're quick with a camera I guess a hat might work?