Well, assuming you're talking about pranks...
As long as I knew it'd be welcome, there are all sorts of little things to do to someone, replace their underwear drawer, slip a change & baby gear, like a pacifier, bottle and whatnot into their bag, gotta sneak in their diuretics into whatever I know they'll drink, could give them a lax brownie too I suppose. Those are the most general options that come to mind first.
No comment on anything being played on myself <w<
