Can't remember if this was urban legend or if it happened to someone here, but...
FA comes thru doing cabin secure, after the standard descent PA. Big group of rugby players who have been rowdy and giving the crew sh!t the whole flight..... the ringleader still has his traytable down. She asks him to stow it and he does. On walking back thru the cabin again she notices the table is down again. Calmly she asks him to stow the table.
On a hunch she goes back to check again just before she has to sit down, sure enough the table is down. FA leans in to the man, just in earshot of his rugby mates, points to the traytable and says "I see you can get it up, it's the keeping it up that seems to be the problem!!"
Red-faced pax stows table amongst hooting and laughter from rugby mates, hostie goes to crew seat with a smug grin on her face.
Classic!!