eMMM's outfit is a doll size Japanese women's uniform, which M. Dot Strange purchased during a Japan trip. There were no doll size male clothes so he choose the only outfit that looks less feminine. He joked that he made eMMM a cross dresser on purpose, and decided that it would be the outfit for eMMM to wear in the movie.
The Sinister Arcade was a game that scared M. Dot Strange when he was a kid, which is why it was commonly shown in the middle of an abandoned creepy alleyway and why it was the only arcade that remained active when all the other arcades were shut off.
Originally the Rain puppet was going to be placed under cape form Ori whenever Ori is in his cape form. But M. Dot Strange decided to have cape form Ori by himself and briefly show that Rain is under Ori in that form.