Based on the pilot, I see no reason why 'Studio 60' can't be a member of Earth Prime-Time, the main Toobworld. Aaron Sorkin's previous series, 'The West Wing' had to be set up in its own TV dimension obviously, since Jed Bartlet was President and not George W. Bush. But at least it wasn't alone in that dimension; 'Mr. Sterling' and 'Smallville' also reside there.
So if 'Studio 60' is part of the main Toobworld, I think it's pozz'ble, jez pozz'ble, that we've already seen one of the characters on another series.
Cal Shanley is the director of the NBS late-night comedy show. But he almost got fired because he left the former producer of the Friday night hit on the air delivering his rant for 53 seconds. (Had he left him on the air for 54 seconds, the new producers would have given Cal a raise.)
But had he been fired, Cal Shanley could always have gone back to his other TV directing job, that for made-for-TV movies.
It looks as though Shanley used his 2005 summer holiday from 'Studio 60' to direct a TV movie starring Brooke Shields. It probably was a fairly smooth shoot, except for one problem - at Brooke's insistence, Cal had to fire Johnny "Drama" Chase who had been playing Brooke's brother. According to the actress, during a tender hug between the two siblings, Johnny got a hard-on while filming the scene.
With 'Studio 60' (the show within the show), Cal shanley may be facing a season full of turmoil and upheaval. So he'll probably take his next summer holiday break and just relax.
'Studio 60'/"Pilot" - Cal Shanley
'Entourage'/"Blue Balls Lagoon" - TV Director
Timothy Busfield played both roles......