bullet goblins

An important rule of gun safety is to treat every gun as if it is loaded.
Bullet goblins are mischievous creatures that put ammunition into unloaded guns when you aren't looking. They love to strike at the worst times possible.

A: Here's my gun with absolutely no ammunition inside it. It's perfectly safe!
B: Careful, man! The bullet goblins could have loaded it!
A: There ain't no way, dude! I just checked 5 minutes ago! *shoots himself in the foot* AHHHHH!