I don't usually watch this show, but while I was looking for a good video about this I realized that my friend did this very experiment to me. I was conditioned to expect an Altoid every day when we would get together to order lunch. Now I get the joke.
An extension of Classical Conditioning that I found fascinating was higher-order conditioning. Higher-order conditioning is when a stimulus that is associated with a conditioned response can also become a conditioned response. For instance, when you are at the park and there is a group of bees on the rock wall. You are already afraid of the bees because you know they sting, then you are afraid to go near the rock wall because you now associate the bees with the rock wall. I never realized that this was classical conditioning.