Fun on the side would be to ask for someone who is willing to become as worth as a bag of Fritos (the 25 cents one), not the meal he may enjoy, and once the quick snack is done, clean up the grease off the fingers, and head back home.
nookie.LOL
To me, "fun on the side" implies that one is in some sort of relationship and is looking to have their physical needs met by a third party. So yeah, nookie.