The film was originally written as Mac and his friends going against the fraternity, but after Seth Rogen's wife read the script, she said that his friends would not care about the fraternity war and suggested writing Mac's wife into the script instead.
The film is titled Bad Neighbours in Australia and the United Kingdom to avoid confusion with the television soap Neighbours (1985). A video was posted on Universal's Facebook page, showing Seth Rogen singing the theme from the show.
The baby turning around to look at Mac and Kelly having sex in the first scene of the film was accidental. The scene was originally supposed to end after Seth Rogen turned her around, however the director Nicholas Stoller noticed that the baby kept looking around to watch Rogen and Rose Byrne, so he instructed one of the camera men to film the baby. According to the director, if you listen closely, you can hear Rogen and Byrne laugh after the baby turns around to watch them.
The university logo on the letter Jimmy sent was said to have the Hebrew phrase "Game over" (Sof HaMisChack) but in fact it a slightly different phrase "the game has ended" (HaMisChack Nigmar) and the Hebrew writing is in reverse.
What characters are referenced in the Robert de Niro party scene?
A
Taxi Driver (1976): Teddy Sanders (Zac Efron) dresses up as Travis BickleThe Deer Hunter (1978): A Delta is dressed up as MichaelRaging Bull (1980): Scoonie (Christopher Mintz-Plasse) dresses as Jake LaMottaThe King of Comedy (1982): A Delta is dressed up as Rupert PupkinCape Fear (1991): A Delta is dressed up as Max CadyJackie Brown (1997) Garf (Jerrod Carmichael) dresses up as the Samuel L. Jackson character Ordell RobbieMeet the Parents (2000) and sequels: Pete (Dave Franco) dresses up as Jack Byrnes