What the Birthday MV should have been
if we stick with the same concept:
a) No characters, Katy Perry as herself. If there are characters, make them good looking and interesting.
b) Surprise the birthday boy/girl and don't ruin their parties
Give the video a positive vibe.
c) Have good HQ footage, not some ****** cellphone quality .
d) Keep the song playing and don't stop it midway through the video.
e) If there are no real birthday parties, hire some actors. That'll do.
So, basically, similar to the Sugar MV
and the fact that it will probably reach 1 billion 
