James Murphy:
During the party scene which Ivan drags Greenberg to, for a brief few seconds James Murphy of LCD Soundsystem walks across the screen staring at his phone.
In the early drafts of the screenplay Greenberg was initially written as a guy in his early 30s. Inspired by the idea of casting Ben Stiller, Noah Baumbach and Jennifer Jason Leigh rewrote the entire script and made Greenberg 40 turning 41.
Many of the actors in this film were first better known as the siblings or children of previously famous entertainment industry professionals: Ben Stiller is the son of comedians Jerry Stiller and Anne Meara; Jennifer Jason Leigh is the daughter of screenwriter Barbara Turner and actor Vic Morrow; Jake Paltrow is the brother of actor Gwyneth Paltrow and the son of producer Bruce Paltrow and actor Blythe Danner; Juno Temple is the daughter of director Julien Temple; Dave Franco is the brother of actor James Franco; Max Hoffman is the son of actor Dustin Hoffman; Zosia Mamet is the daughter of actor Lindsay Crouse and writer David Mamet.
The clothes worn by Greenberg, Florence and Ivan in some scenes include sweaters and jackets that would normally be too warm for Los Angeles, especially when some other characters are wearing swimming gear.
In the final scene just after Roger received the second doll he walks screen right. As the camera pans with his movement, it appears as though the camera is visible in the bathroom mirror at the back of the scene.