It's a penis phoenix.
This song is quite honestly a work of genius. Amazing guitar work, in a classic 50's-style blues rock, with references spanning the history of rock as we know it. One of my personal favorites from Tenacious D's nes album, Rize of the Fenix, which was just released yesterday. As you can hear from this song, the lyrics on the new album are very clever, and very funny when you think about what Jack is singing, but they are not drop-down funny or explicit. It makes for some awesome songs, but much less humor than one might expect from the D.