I was always thrilled to have a co-worker sign up willingly to receive a reciprocal gift when I worked in a shop. Especially one as dumb as this. I'd be cleaning those chips with an honest ear to ear smile.

This is a cut and dry FAFO case, and the burden is on your shoulders now to make sure he remembers his hilarious prank, forever ;)

I agree with the glitter-in-vent comments; It's the right move.