Before or after seeing it, you might want to take a look at the "Undeclared" episode called "The Assistant." It's on the DVD, and has been posted piecemeal on YouTube. The first part is here. When you link to that, you'll see links to the other portions.
It's of note because part of it has Adam Sandler, Seth Rogen and writer-director Judd Apatow working together. Sandler and Rogen co-star in "Funny People," written and directed by Apatow; the Sandler-Rogen relationship in "The Assistant" (co-written by Rogen and directed by Apatow) echoes in interesting ways in "Funny People." In addition, in the movie Rogen's character works as Sandler's assistant, and there's some comedy built around Sandler's dealings with his assistant on "Undeclared."
The DVD version has audio commentary by Apatow and Rogen which, among other things, makes clear their disdain for HBO's "Entourage" and for Fox, which aired (and after a single season canceled) "Undeclared." And some comments by Apatow about the respective acting styles of Sandler and Rogen which is reflected in their characters in "Funny People."
"Look at the clash of styles here," Apatow says during a scene between Sandler and Rogen in "The Assistant." "[Sandler is] Natural, a star, carrying himself, knowing what he does, knowing who he is. [Rogen:] Young actor, scared, terrified, mugging up a storm."
Also, Rogen says he knows RZA, who has a small part in "Funny People."