We have a neighbor cat that is just a year younger than Sid and they played together when they were young, so he thinks of himself as a part-time member of our family. He used to come in to get some of their food (this guy mooches off of a lot of people - and yes, his humans know, I woudn't feed someone else's cat without their knowledge)

Anyway, so we made a game out of it and made him do a trick to get his food. He would have to turn in a circle two times to get his treat.

Then one day, he wised up and looked at us as if to say "Enough is Enough - I'm not doing your stupid trick anymore - and yes, you WILL continue to feed me!"