You call shaving cream on the hand a prank? VANILLA! (just kidding) Idk. I guess we were bad kids when I grew up because we would hack each other's runscape accounts and stuff and drop each other's stuff or transfer it to a fake account and hold for IRL ransom until somebody made you breakfast or something along those lines. Or we would watch somebody type their password on their laptop and if we caught it we would put a gross or lame picture on the desktop. I think if anything it actually built trust and friendship between us. Of course there was some drama once in awhile or you'd really make somebody mad, but at the end of the day we all stayed friends, and still are over a decade later. We had a lot of laughs, but it was like, ok who has the group not picked on recently? Time to prank them.

So while I understand in cases like yours it can be bad, I think calling for legal action and generally freaking out about it as a general rule is pretty lame. Kids will be kids. Shit happens. Life happens. Don't let people use your computer.