From Mark Hoppus' AMA on reddit, roughly 3 years ago:
Q: What was the first song you guys, as blink-182, wrote and thought "we sound pretty good; we could make something out of this"?
A: carousel. we wrote it the very first time I met Tom. I showed him a bassline i'd been working on, and it fit perfectly with a guitar part he'd been working on. We'd only known each other for less than an hour and the song was fairly formed even then. it was weird.