I heard. :-)He thinks they favour slapstick.
Well, it'd have to be pretty broad humour for a human observer to tell that something's meant to be funny. I mean, cross-species communication being what it is, he can't exactly show them Fawlty Towers
and then listen to them yelling "SIBERIAN HAMSTER?" and "HE NAMED IT BASIL!" and twittering with laughter.
There are probably all sorts of little subtle things rats find funny that we can't interpret, like "he held his tail at *what* angle?" and "*the* most absurd smell, I'm telling you!"
I can remember my first three rats and how they used to interact. There was an evening when Vlad and Oz were having an, um, leadership discussion, and Oz (little guy, specialised in flying leaps and using his momentum against the opponent) backed up and slowly sized Vlad up like he was about to do a big pounce. The tip of his tail twitched. Everything goes very still. Then Oz elaborately yawns.
Francis (Vlad's brother) was sitting on a ledge, and I think he was watching the play with the same fascination and amusement that I was.