Kinda hard to do when you are expecting it.
I had a prank in mind years ago I planned to do for my young daughter, but when I found out how much a sheet of clear plexiglass would cost I had to scrap it.
I wanted to convince my daughter I got sucked into the tv. Even very young she was a smart cookie, so just playing a recording would not suffice. I wanted the plexiglass to knock on and press my face against to make it more believable.
I did prank her once with a massive quantity of balloons stuffed in her room. After a few hundred, tying them off made my fingers terribly sore. It was just over knee high! I would not have gotten that far were it not for the use of my air pump.