In a D&D game I was playing:
Player: I want my kobold to steal the eggs of the giant centipede we just slew.
DM: You're lowered down into the lair, and see the clutch of eggs covered in webs. What do you do?
Player: I cut the webs and take an egg.
DM: You are immediately attacked by three giant spiders.
Player: ... I forgot centipedes don't spin webs.
I had to draw it.