Several dozen brunette, redhead, and blonde girls were facing execution via firing squad. The firing squad took the brunettes first, and the leader said "Ready, aim ... " at which point the brunettes yelled "Earthquake!!!".The firing squad looked around anxiously and while they were trying to figure out whether there was an earthquake or not, the brunette girls all took off and escaped.
Undaunted, the firing squad took the redheads next, and the leader again said "Ready, aim ... " at which point the redheads yelled "Tornado!!!". The firing squad looked around anxiously and while they were trying to figure out which direction the tornado was coming from, the redhead girls all took off and escaped.
The firing squad took the blonde girls last, and by now the blondes had it all figured out; when the right time came just yell out the name of some natural disaster. So when the firing squad leader said "Ready, aim ... ", the blonde girls all yelled out "Fire!!!".