The comedy was written and is to be directed by "Knocked Up" and "The 40-Year-Old Virgin" filmmaker Judd Apatow. Both of those films also featured Rogen and Mann.
Apatow and Sandler previously collaborated with Robert Smigel to write the screenplay for "You Don't Mess With the Zohan."
Hill co-starred in "Superbad," which Apatow produced, and had supporting roles in "Knocked Up" and "The 40 Year-Old Virgin."
Variety.com said Apatow hasn't revealed details of the plot for "Funny People" and will only confirm that it takes place in the world of stand-up comedy.