There were, in fact, two Legend of Zelda rap commercials — the one mentioned above, and…well, and the other one. Apparently, at some point, the ad wizards at Nintendo decided that bizarrely choreographed rap was just the thing needed to sell games. Maybe it was. I myself was swayed by just about any advertisement I saw at that point in my life.
Anyway, of these two commercials, the one I've seen was advertising Link to the Past, and aired on Japanese television. It's set in a smoky dungeon, with the usual complement of Zelda villains — Wizzrobes, Stalfos, Keese, and the like. A surprisingly Japanese-looking (I could swear that she's blonde in game canon) Princess Zelda is trapped in a cage, and a similarly Japanese-looking (ditto) Link is outside of it. The only difference between this and all other Zelda scenarios is that…everybody is rapping. In Japanese. And it's early-1990s rap: the painful kind. Adding to the general weirdness, the actor playing Link is actually an actress.
Link raps for a while and dances around, and then starts to fight people. Although the advertisement is for a Super Nintendo game, it sounds like the actual snippets of the Zelda theme music we hear are from the NES' synthesizer. Don't ask me. Anyway, the Wizzrobe tries to shoot Link; he dodges. A couple of knights charge him, and he holds his sword out and starts spinning wildly (a common fencing technique). Finally, he plants his sword into the ground, and powerful magicks knock everybody to the ground and cause a statue to fall apart.
With his foes vanquished, Link opens up the cage, and he and Zelda share a frightened embrace as Ganon appears. That's when we cut to a high shot of everybody dancing in formation, including Link, Zelda, and a bunch of people wearing black jumpsuits with skeletons painted on them. Everybody's chanting what sounds like "go, go, go, go!" at this point as the dungeon crumbles around them, oblivious to the gigantic magical pig about to eat them.
Oinking noises are heard over a fade-out. Cut to the Nintendo logo.
If you don't believe me, you can check this out for yourself at http://gameads.gamepressure.com/tv_game_commercial.asp?ID=2689.
If anybody could help me translate the commercial, that would be super.
An addendum: Link is, in fact, casting the Quake spell when he spins and plants his sword. Meum malum. Thankings to rootbeer277. | 
