At the roller disco, the owner says she received a telegram from the IRS indicating they need $85k in back property taxes or they will have to shut down. Property taxes in the US are generally paid locally, and notification would not have been provided via telegram.
About 20 minutes after the start of the movie, Tux is showing his girlfriend the "Tuxes' Magical Trail Mix." Immediately after, the scene cuts to a group of skaters dancing. When the camera pans up, you can catch a brief glimpse of "The Simpsons" arcade game, with Lisa Simpson's face appearing on the game screen. The movie is set in 1976, but the Simpsons arcade game didn't come out until 1991 and that the actual show didn't come to existence and popularized until 1989.
Movie set in 1976 has a character form that era refer to the 1981 Rick James hit song "Super Freak".