Just have him choose things he knows about so he can ask you questions.

I would be characters that he knows. It could be like cinderella and and x-men arguing about keeping the toilet seat down.

Characters from tv, movies, books. Then create a funny disagreement between them.

For ex- You leave your glass slippers all over the place so whats the big deal if I leave the toilet seat up!?

He may be too old but fairy tale characters mixed up are also funny.

For the set, put a few chairs together and get something to be a microphone. Maybe a box of tissues would be funny. Ask him what HE wants

Goodluck

Oh, if you can secretly record the show, you can have some fun with this at his wedding.

you should just sit on the couch and talk as if your famous people like he could be a footballer or something and you could be a popstar or actress something like that