The line "what is this, garbage day?" is a reference to Silent Night, Deadly Night Part 2 (1987) when Ricky (while on a shooting spree) says the infamous line "garbage day!"
The film was partially inspired by the real-life Covina Holiday Massacre which took place on Christmas Eve in 2008.
Most of the characters are named after members of the famous Leeds United football team from the seventies: Cooper, Giles, Madeley, Revie, Jones, Jordan, McKenzie. In addition, Bremner St and Reaney's Diner are mentioned in the script.
There's a scene where an elderly man wakes up after not talking for a year to warn his grandson to "watch out". This pays homage to the original 1984 "Silent Night, Deadly Night".
The film's Wisconsin setting is a reference to the protests of the original film, which were centered in Milwaukee.