Gnamp's Boot Fingers (the old body-in-the-trunk gag)
Classic practical joke- popular in the 1980s
Amusing, but definitely not advised to pull this one these days I'm afraid. (Modern times, eh?)
Always choose your audience wisely; which is of course not an easy thing if you aim to go about doing stuff public-wise.
Look- don't be surprised and certainly don't blame me if some hero tries to rescue your 'captive' with a steel crowbar or the cops spoil your day for making them feel silly.
Just put them on the fridge door, toy-chest or laundry hamper for now- or wait to see if things lighten up socially- then you can fill your boots, so to speak.