PATD has got an interesting range of music -- all their albums sound really different to each other. The first album is really pop-punk with emo lyrics, the second is like a modern 60s-psychedelic pop-rock, and the third is alt-rock with heavy 80s/new wave pop influence.

But if you only listen to one song, listen to It's Almost Halloween. I dunno, I find it insanely fun to listen to, and even though it's very Beatles-esque (and I'm not their biggest fan), it's still catchy and great. =D