If he had done it with someone else I would've pointed out how they could've glued their hands to each others head so it looked like they had pulled off the other persons head instead, but never mind :P
I'll probably get flamed for this, but if he wanted to do it properly he should of glued his hands to his head so it looked like he pulled his own head off when it disengaged from his body.
Speaking of knives, a car came in to work today for an MOT, and just casually placed inside the drivers door compartment was a 7 inch serrated knife, we had to nominate who would tell the bloke his car failed on the MOT