Circle the Drain is good but it would have flopped as a single, it's too experimental~ for Katy's radio audience.
OoTB is the best example we have of her doing rock influenced music.
Hmm, I guess I'll have to try to check out OoTB, I've only listened to her singles from that album and the title track (which I didn't care for, and thus didn't bother to listen to the rest of it). Do you have any recs?