Late in the movie, they screwed up by alluding to 'Elvis'
Obviously in the universe inhabited by this movie, Elvis Aron Presley and Jesse Garon Presley did not exist.
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4) You ever seen Superman $#$# his pants? Case closed.
I was pretty shocked too... but it's presumably in purpose. It's sort of a safeguard against any royalty claims: no no, the character isn't Elvis, see, Elvis even exists in this universe!
I hope this has taught you kids a lesson: kids never learn. Chief Wiggum