This song doesn't describe me, but I love it and have been listening to it a lot lately. I can't stand any Radiohead outside of Ok, Computer and Kid A, but those two albums alone are total brilliance.
I'm a quiet guy, and not very cheerful either but if you listen closely then there's a lot more going on than what you see on the outside. (I'm also [censored] insane, but it's hard to find just one song that describes all those things)
I'm not sure if it describes ME, but it definitely has this vibe of happy-go-lucky chaos that I tend to seek out. The heartiest laugh is with a mouth full of blood.
I usually don't find any songs that really describe me at all, the best that I can come up with is what I call my theme song- Driving My Life Away by Eddie Rabbitt.