Not one of my more extreme pranks... but it's my favourite because it was thought up on the spot within seconds..
On holiday in spain a few years back and we saw a family get into one of the lifts...
So we got someone to stand by the door to see what floor they were going to so we could run up to it and seat ourselves on the idential seating arrangements.
Got their floor, run up to it mentally fast.. sat down and waited for the door to open... as it did they started to walk out the lift.. thinking they hadn't moved they got back in and went back down to the first floor
Don't think i've laughed as much when we ran back down and did the same thing again..
I'm brilliant...