In the special edition DVD commentary Judd Apatow had his nine year old daughter with him. He asked that no one swear in front of her. Jonah Hill swore a number of times angering Apatow. After an argument, Apatow left the commentary with his daughter.

# # Emma Stone's (Jules) reaction to getting hit in the head by Jonah Hill (Seth) was improvised. At the end the writers decided to keep it in the final cut.

The bartender in the scene with the cops and Fogell is played by Ted Haigh, the graphic artist.

The guy who punches Fogell and robs the convenience store is played by Tim Trella, the stunt coordinator.

# # According to the DVD commentary, the night that Evan (Michael Cera) describes to Becca early in the movie is "beat by beat" what Seth Rogen, Evan Goldberg and their friend Sam Fogell did when they were in high school.

Justin Long had a scene in the movie that was omitted due to length.

The 1970s' version of the Columbia Pictures was shown at the beginning of the film, instead of the present version of the Columbia Pictures logo.

The "semen conversation" was mostly improvised, and lasted for about 4 minutes. It was edited to under a minute for the final cut.

When Evan is at the party where all the people want him to sing for them, one of the party goers tells him that his friend came from Scottsdale, Arizona to be at the party. Emma Stone was born in Scottsdale, Arizona.

Film prints were shipped to some theaters under the name "Separation Anxiety".

Because Fogell (Christopher Mintz-Plasse) was only 17 at the time of filming, his mother was required to be on set during the filming of his sex scene.

In the scene in Evan's bedroom, Evan is playing as Sergeant Ben Mitchell in ‘The Getaway: Black Monday’, a popular Playstation 2 game set in London. This game is exclusively for the PS2.

# # During filming of "Undeclared" (2001), Greg Mottola had a table read for the script with Seth Rogen reading for Seth and Jason Segel reading for Evan.

Water was used for vodka, apple juice for hard liquor, and non-alcoholic beer was used for the party scenes.

The pivotal penis drawings were a 'bone' of contention with the MPAA, particularly the scene with young Becky holding an image of one of them. Producer Judd Apatow elaborated it was the subject of much legal wrangling, including how erect they could be, if veins could be shown etc. The actress playing young Becky, Laura Marano, however has a different picture to hold before we cut to the actual drawing. You can even see from the reverse that the drawing she holds appears completely different.