haha! so i guess the proper translation would have been "you've been punk'd!"
man, i remember the vma awards last yr where chris rock pointed out that ashton kutcher never punks rappers... man that joke was so hilarious at the time.
neways.. eurasian's right in saying "dokkiri" is what they say after the prank's gone through, which to try to explain it further (no it's not a made up word.. or it could be like one of the words that pop culture has made up but now actually has meaning in japanese) they took it from "dokki" or "dokitt" which is like.. kind of an onomatopoiea (dunno how to spell that and too lazy to look it up) for like when the heart momentarily stops, or you get shocked or that kinda stuff. sorrie i'm not too good at explaining but yeah. so the tv shows use that word coz it's like, we surprised u and ur heart stopped for a bit kinda thing.