Step 1: Sit down next to them anyway, smooshing their bag between you and them.
Step 2: Wait for them to give you a really dirty look.
Step 3: Lean over and say, "You are making the baby jesus cry"
Trust me and try it sometime...it is a lot of fun. I won't spoil the results for you.
On another note of me being a complete ass.....
I ran into my upstairs neighbor the other day in the hallway, the guy who lives with his girlfriend directly above me.
Him: You live in 3A below me right?
Me: Sure do.
Him: I hope we are not too noisy, or stomp too much.
Me: Nah, you are good, but do you have a headboard on your bed?
Him: (grinning in that guy-to-guy "I am a stud" sort of way) Oh yeah....loud huh? Sorry about that.
Me: No worries, it does not last long (as I entered my apartment).