Boong Ga Boong Ga is a Japanese arcade game where you physically jam a big cartoon finger into the plastic replica of a woman’s butt, and watch the screen as her animated face contorts with surprise and, uh, whatever.
You’ll also see what are allegedly the game’s mascots in costume form: a big foam hand with extended finger and a walking turd.
(And in passing, I should note that below that is a mascot from a Japanese Playstation 2 video game, where you control a vacuum cleaner and try to pull the shorts off of monkeys. The game is available in the United States, though only for Japanese-made PS2s.)
There’s a tamer variation intended for the U.S. called “Spank ‘Em!” where you spank the plastic butt instead. The images below are flyers from the manufacturer; the second is in English and well worth looking at. In “Spank ‘Em!” you get to spank all sorts of villainous types, including ex-boy/girlfriends, con artists, and of course child molesters. Ah, the relaxing joys of videogaming!