The format of a Senior Demon advising an Apprentice is directly inspired by C.S. Lewis' 1942 book "The Screwtape Letters"
The gas station's intentional graffiti was painted over during production (presumably by a city cleanup initiative) and had to be restored by the film crew to its previous look so that filming could resume
In addition to the literary reference to "The Screwtape Letters," Derrickson also drew inspiration from Wim Wenders' film "Wings of Desire" (1987) where two angels wander the streets of Berlin, observing the lives of humans and trying to quietly help the distressed or lost. The two demons here are an inverted version of that premise
The title card quote is attributed to Paul David Hewson, which is the real name of Bono, the lead singer of U2
At the time, Led Zeppelin famously did not allow their music to be licensed for use in a lot of media, and never for fees smaller than a fortune, and most certainly not for free to a student/short film. The only reason Derrickson got permission to use "Kashmir" for the end credit sequence was through his persistent requests: he telephoned so repeatedly that, eventually, when the rights-holder took a call while he was on a boat on vacation, he granted the license to the song just so Derrickson would finally leave him alone.