A game where people add or use the phrase "In my pants" as a supplement or to replace part of a sentence. This should not be done in a conversational group of sentences, because it is just plain stupid. You should use movie or song names, common phrases, lines from songs, or well known quotes. The object is only to make each other laugh. Be creative. Can also be done with the words "between the sheets".
A: "Spice up your life" in my pants
B: Haha! "Welcome to the jungle" in my pants.
C: How about... "10 things I hate about you" in my pants.