Two things:
In comedy, there is something called the "rule of threes". For this movie, it would mean that "cock joke" was funny the first three times, but not the fourth or the fifth in the credits.
Secondly, it's "P.P.S.", not "P.S.S.". The "post" in P.S. means it's after everything, so you want it to say it's after the post you already made, so you would say post-post script, not post script script. Get it?
Nevertheless, I enjoyed the movie. Great idea, and good animation.