You must be single...

This is a joke that is just fantastic to tell in person. You build up this elaborate grocery list, making every item seem significant. Take your time. It works even better if you have someone else who knows the joke. One of you can remind the other of items, then say "of course, can't forget that." Then, instead of just "she looked over her items," go through the list again. The listener starts trying to make connections, trying to figure out where the humorous connection is between all these items that will somehow add up to singleness. They're thinking that this must be one of the most in-depth jokes ever told.

"Because you are ugly."

/r/Jokes Thread