There is no escaping marbles!!! What I mean is, if you'll get a bag of marbles, put them in the freezer & throw them into the bed with him, it'll wake him up every time!! No matter where he tries to move, the marbles will roll on him!!!
take the head of a mannequin of a creepy guy and put it in bed next to him and gently wake him up and let him see it.if you don't like it, then look on youtube, there a lot of great wake up videos on youtube.
If he plays Slender, you should dress up as slender man, then get in the room, if he has a TV, then make it all staticy, and turn it up, and if he wakes you just stand there, and he will get so scared he will crap his pants!