Bands that came up fast (and then stayed big).

I was living in Nashville when Kings of Leon popped up out of nowhere, nobody in town knew who the fuck they were. They just materialized out of thin air.

Eh, Arcade Fire had a debut ep (the one with 'No Cars Go') and were a steadily touring/opening band for at least a year before Funeral. I saw them open for the Constantines in 2003. Hype rose up in Canada on the basis of that/college radio.

I imagine alot of boy bands fit this trope; either they get big fast or you never hear of them, and if they get big they often stay big for a few years. A longer run, though, is difficult for obvious reasons.

Westlife