According to the film's actors and director Nicholas Stoller, the twin girls Elise Vargas & Zoey Vargas who played Stella were incredibly well behaved and were always smiling and happy. The only time one of the babies became upset and started to cry was when Seth Rogen and Rose Byrne yelled at each other while filming their fight scene.
Olmsted Drive and Officer Watkins are named for buildings at University of California, Riverside.
The guys throw a party based around various Robert De Niro film roles. Lisa Kudrow (Dean Gladstone) starred alongside De Niro in Analyze This (1999) and its sequel Analyze That (2002).
Olmsted Dr and Officer Watkins were allusions to University of California, Riverside since two of the buildings bear the names.
The pledge that the fraternity brothers take is the real life pledge of Sigma Nu Fraternity.
The entire cast and crew became very attached to the twin baby girls who played Stella. The entire cast and crew went to the set on the babies' last day of filming so they could say goodbye to them.
The film is titled Bad Neighbours in Australia and the United Kingdom to avoid confusion between the film and the television soap Neighbours (1985). A video was even posted on Universal's Facebook page, which showed Seth Rogen singing the theme from the show.
The final scene between Mac and Teddy outside of the Abercrombie and Fitch store was completely improvised. Zac Efron had no idea that Seth Rogen would take off his shirt.
According to the film's actors and director, the twin girls who played Stella were incredibly well behaved and were always smiling and happy. The only time one of the babies became upset and started to cry was when Seth Rogen and Rose Byrne yelled at each other while filming their fight scene.
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.
This film opened in the UK on a Saturday - 3rd May 2014 - instead of the normal weekday opening day of a Friday. A number of UK cinema outlets started their first showings at midnight or a few minutes after midnight.
The film earned its production budget back on the first day of the film's theatrical release in the United States. The budget was $18,000,000, and the film made $19,574,490 on its opening day.
Became the fourth largest R-rated comedy in history after its opening weekend total of $49,033,915.
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 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.
All of the actors took major pay cuts in order to help save money for the budget, in particular, Seth Rogen and Zac Efron.
Nick Offerman and Megan Mullally - who are a couple in real life - filmed a cameo as Christopher Mintz-Plasse's parents, but their scene ended up being cut from the final film.
Was originally titled Townies, but was changed to Neighbors.
On the day he was supposed to film his love scene, Dave Franco got a blemish on his butt and had to go to the make-up artist and ask if she could cover it with make-up.
Zac Efron broke his hand during his fight scene with Dave Franco. The writers and producers were panicking and started to plan how the broken hand would fit into the movie, and how much the budget would change. However, they were surprised to learn that Efron arranged an emergency surgery so he could be back on set one day later.
Seth Rogen said that the baby eating the condom made him laugh till he cried.