found this online regarding the Yatta thing:
"Say, let's us post a wacky video from Japan and then generate a bunch of spurious explanations for it without bothering to ask the poster who lives in Japan. Shall we? Let's! Okay, that said:
"The group's name is not Pony Canyon- that's a distribution/production company or something. "Yatta" is more or less the work of a comedy duo called "Ucchan-Nanchan" (after the two guys' names: Uchimura and Nanbara). The have a tv show that's sort of half variety-show, half sketch comedy, and "Yatta" started out as a sketch on that show. The sketch was about a mythical music group called "Happa-tai" (Leaf Squad, more or less- that's what it says between "Yatta" and "Pony Canyon" at the beginning) where all the members wear only a leaf and sing this happy song called "Yatta" (literally, "I did it", figuratively "Yeah" or "All right!" It's what Chun-Li says when she wins). It was just absurdist, there's no deep meaning. "
"The guys in the group are Ucchan and Nanchan and the regular cast of their show- a comedy trio called Neptune and some other guy I don't know. Anyway, Ucchan-Nanchan kept reviving this sketch in different ways, as sketch comedy shows so often do, and eventually got to the point where they made a music video and would occasionally appear on other shows as the Happa-tai. This particlar clip is probably something from the regular show, but its all a gag- picutre an SNL music video starring the Coneheads. "