He was a boy/She was a girl/Can I make it any more obvious?
Give Avril a little credit, here. At least she hasn't been sued for plagiarizing this particular song. That's not to say she didn't steal it, of course ... it's entirely possible she did, and the original writer just has enough self-respect not to take credit for this affront to music.
Avril answers her own question here somewhat, since the very fact that she keeps singing indicates that she felt like she needed to elaborate. If the answer was "No, this cannot be made more obvious," then the song would presumably cut to abrupt silence at that point, which would improve it by a factor of 10.
Though, even after having listened to it, we're still not completely sure what was supposed to be obvious about the line, which merely stated the genders of two people. We had assumed the rest of the lyrics would be Avril backing up her assertion with detailed descriptions of their male and female genitalia. That's how the Black Eyed Peas would have done it.
Or, perhaps Avril's "obvious" message is simply that she's an atrocious songwriter. If so, then mission accomplished, Avril.