Classic pranks to play on a sleeper include putting shaving cream on his hand and tickling his nose or getting creative with makeup and drawing pens. A sleeping person is an ideal foil to play a prank on because of his sheer defenselessness.
Depending on the prankster's levels of viciousness and the sleeper's ability to take a joke, one of the most vicious tricks is to randomly shave various parts of the victim. A missing eyebrow or chunk of hair is hilarious to bystanders, but maybe not so much to the sleeper.
Another popular trick is to pose the sleeper in a variety of unflattering angles and take a number of selfie photos. Posting the selfies to social media increases the cruelty of the trick exponentially.
If the victim is a very sound sleeper, transport him and his bed out into a public area and prepare to take video of the moment he wakes up to discover that he is no longer in the safety of his room.
Tamer pranks include using plastic wrap to secure the sleeper to his bed and setting alarm clocks an hour early to make the victim think he is late for school or work. An old trick is to hang a spider just over the victim's face and watch him scream when he wakes up.