You know, I really dislike much of Katy Perry's most popular songs. In particular I feel that the end of the hook (the "answer" to the beginning of the phrase or the "subject") squanders the build-up from the verses through the bridge and into the chorus. And it does so by leading you up and up... until she finishes off with an "oh aeh oh eh oh" like nobody could figure out what else to put in there. No, man, that's the part of the song that has to deliver -- that's not the place to cop out.
Anyway, so yeah. Drew has issues with the bulk of the Katy Perry oeuvre.
I did, however, enjoy "I Kissed a Girl" The answer to the subject in the chorus is adequate. And, you know, it can be done in different styles which is also amusing.