The actor playing the Repigeonator, the main villain, is RaisorBlade, the first film critic who reviewed the director's/writer's/producer's first film, 0000: A Shark Odyssey (2018).
The Repigeonator was originally killed off at the finale at the TERFhole. However, after recording RaisorBlade's lines, Iki Ènèng liked his performance so much that he wanted him to return for the sequel, so he inserted the post-credits scene, where the Repigeonator is alive.
The 3D model used for the deer running in front of the characters' car is the same used for the character Hirvinauru in 0010: The Sharks Make Contact - Part 2 (2019), even though Hirvinauru doesn't appear in this movie.
The train route in the opening scene, particularly the bridge over a bay, is modeled after the Northeast Corridor route between Washington, D.C. and Philadelphia, Iki Ènèng's favorite route in Microsoft Train Simulator, which he used to play a lot.
The twist at the end only came to Iki Ènèng's mind when he wrote the scene. Originally, this was going to be a complete standalone movie.