Pranks for roommates?

Question

I was away for the weekend and came home to a prank done by my roommates. There were at least 50 water filled condoms in my sink, and 10 others around my room/bathroom. I suck at pranks so what are some good ways I can prank them back? nothing that will destroy anything, just something harmless that will get them back.

Answer 1

Inject Tabasco sauce into their Toothpaste tubes,
Place small water balloons in the toes of their boots.

Answer 2

cover all of their furniture in plastic wrap. cover their car in post it notes. fill their bed with grass.

Answer 3

Gimme some background on them...I will be only too pleased to help!

Answer 4

Take a dump in their bed. It works best if they're in the bed at the time.