I guess it's physically impossible for you to get Dance Dance Revolution for your iPod, but this might be as close as you can get. It's Musika, a pseudo-psychedelic new game from PaRappa the Rapper creator Masaya Matsuura of the Japanese gaming company NanaOn-Sha, and it's just been released for 5th-generation iPods in conjunction with Sony BMG Music Entertainment. You can buy it in the iTunes Store's game section.
It's a "visualization game," so you can either watch the pretty patterns that synchronize with your iPod's current tunes, or you can use the center button of the media player to "play along" by matching letters found in the song title (or something like that). Basically, it's an aesthetically-pleasing time-waster that sounds like it'd be fun under the influence of certain unspeakable green substances. No word on what it'll do to your battery life.
Musika is clearly in the vein of trippy post-Tetris puzzle games like Lumines, except instead of a corny techno soundtrack, you can use your own phat beats. A cool concept indeed, but early iTunes reviewers have given it lukewarm reviews: one said it was "entertaining for minutes...not hours." For $4.99 in the iTunes Store, I suppose it's worth a shot if you need something to do besides get the munchies.