When Frank is buying the AK-47, the dealer describes it as "The very best there is. When you absolutely, positively got to kill every motherfucker in the room, accept no substitutes." This is the same way Samuel L. Jackson's character describes an AK-47 in the beginning of the Quentin Tarantino film Jackie Brown (1997).
During the news of the theater shooting at the bottom of the screen you can read about Libyan terrorist fouled attempt at obtaining plutonium bars. A nod to Zurück in die Zukunft (1985).
Steven Clark was based on the real American idol contestant William Hung, who's audition went viral and was mocked to the point of making him perform on stage in the finale. He didn't know they were mocking him and laughing at him. He believed they were cheering him on.
An hour into the film, Roxy and Frank discuss their shared view of Alice Cooper. Roxy goes on to state that Cooper was the first to dress in women's clothing, wear make-up, etc., all before David Bowie. This is however, incorrect; Bowie's career and fashion launched itself a few years prior to Cooper's music career. The New York Dolls also dressed in women's clothes and wore makeup prior to Cooper.