The movie being shot during "On Set" - "As Time Goes By"- is actually a screen-play written by Ryan Redmond. The Writer/Creator of On Set.
The actors who play Ryan & Charlie were actually roommates for a short time when they first started working in the industry. They actually did share a closet for three months.
All 10 episodes of season one were shot in 10 days over the cast & crew's holiday hiatus.