What is fun for pet rats besides food?

My friend is having a rat birthday party on Thursday. She is going to have some treat food (please don't say not to give them treats because they get a good diet and one day of treats won't hurt). We are trying to think of ways they can have fun. We are making a maze already. What are some cheap ideas? No saying rats or stupid!!!!!!No one sentence answers that say something like "Going to a concert," either!

1.)Pinata-Get lots of pieces of kitchen roll and wrap their favourite treats up in it then tie together with cotton and hang somewhere.2.)Pea fishing-Get a bowl of cold water. (Not to deep as rats can't get there ears wet!) Drop some frozen peas into the water and let them fish!3.)You could simply wrap some treats up and give them to your ratties.4.)Place a few treats inside your maze and let them find them!( A good website is www.dapper.com.au)Hope that helped and hope your ratties have lots of fun!