I love those shirts.

I saw one that had a picture of a cow on it. Then there's a little balloon coming from the cow's mouth that says "Woof." That one would be fun to wear to therapy....
In response to the original question, there is occasional comic relief in my therapy sessions, just in the form of jokes that T and I will make (mostly T). My favorite was when he made an analogy about walking through a pasture avoiding cow-pies. I told him his analogy was "very deep."
Sidony