Actor Charles Fleischer, best known for playing Roger Rabbit, has the small role of Allen from Mr. Chompers. According to the book, Permanent Midnight, Jerry Stahl wrote an unaired television pilot as a vehicle for Fleischer.
The fictional television show "Mr. Chompers" was based on author Jerry Stahl's experience writing for ALF (1986). The other television series was based on Stahl's experiences on Twin Peaks (1990) and Moonlighting (1985), and its star was apparently based on Cybill Shepherd.
When Jerry is at the methadone clinic, the doctor is checking boxes on a form he's filling out. The questions he asks Jerry do not match the boxes he checks.
After Jerry picks up his daughter from Sandra to babysit her (at approximately [1:01:40]), he can be seen driving down the road sitting on the right hand side of the car. This is not consistent with other scenes in the movie and furthermore, the driver is clearly not Ben Stiller.
Jerry: You know what's mortifying? Smack is like the leisure suit of the nineties. Instead of wrecking dad's Buick on prom might, these little suburban fucks are coping habits and OD'ing in the rec room.