Raven's Clown Outfit in the Final Scene is the same clown outfit that was used in the original short film version.
Throughout the film, Matthew placed loads of Easter Eggs from past films, In Anthony the Scientist Scene you see body parts from past MMH Production Films, Bottles, the ripped face from Easter Massacre and so many more.
The original script called for Anthony the Scientist to hum in the beginning while working on his experiments, last minute it was changed to the scientist playing a violin as old music plays from the vintage radio.