They're the only as The Rolling Stone put it "Nerd Rock" band out there.
weezer sounds like 'the rentals'.
pixies, nirvana, a little bit of Green Day
They are original, but that doesn't mean they can't REMIND you of another band. The Cars and The Beach Boys are very similar. In fact, mix those two bands together and you'd have a very Weezerish band.
but really, i don't really associate weezer with other bands in my head.