The week my sister got her driver's license there was a report of a man that hid in the back of a ladies car and when she went to get a fillup the service attendent noticed him and told the lady she needed to sign something - he then called the police and the man was arrested.  This was all over the news.

Anyway my sister was going to the store to get something and I climbed in the back of her car and hid - when she started the car I popped up - She really freaked out - I told her she should always check her back seat. She still remembers that.

I worked in an large office after college and another guy and myself were always playing pranks - the final straw came when I went to the pet store and bought a mouse and put it in his desk.  I think he flipped his chair over trying to get away from it.