Given on someone's birthday, this involves tying down the recipient and attacking them with tentacles shaped like giant penises, followed by urinating on them. While this may sound unpleasant to the average person, there are at least 20 different hentai mangas devoted to this very subject.
Geoff: Happy 22nd, Jamie! Now it's time for your Japanese Birthday Surprise!
Jamie: Japa-what? What the hell are you... oh my god AGGHHHHHHHHH