A pie to the face is inherently funny. A pie-to-face variant involving propellant gas, a hidden cameras, and a Japanese studio audience is just the greatest cheap thrill you'll see all week.
What is it about a trap door that compels the subject to peer inside? In this age of whimsical technology and pervasive paranoia, isn't it just so human to stare curiously into the void, expecting anything other than catastrophe?
Yup. Human, all too human.