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When Isaac is tripping out in Mr. Green's car, he hallucinates that his daughter works in a strip club when she grows up, and his wife blames it on not "reading the books." Seth Rogen previously was in Knocked Up (2007), where his character got in trouble with his girlfriend for not reading any of the baby books, and his character was also afraid about the kid he was about to have.
Director Jonathan Levine revealed on Collider that a lot of the film's comedy was improvised, and the dramatic moments were per the written script, which he admitted was more like an outline guide.
In the limousine, Isaac, played by Seth Rogen, calls Ethan "Joseph." Ethan is played by Joseph Gordon-Levitt.
Some of this movie was filmed in August. The cast said they felt really hot in the Christmas sweaters they had to wear outdoors in summer.
There are many references to Die Hard (1988), including a character who likes to imitate Hans Gruber, the music to Ludwig van Beethoven's 9th Symphony, and characters singing Run-D.M.C.'s "Christmas in Hollis."
The nude photos were provided by a body double.