Our favorite sitcom writer who doesn’t know us has some excellent advice about sitcom format. (And, no, we don’t know what the picture has to do with it. You’ll have to ask Ken. Tell him TVWriter™ sent you.)
Advice for Young Writers
A question I’m always asked is:
If I’m writing a spec script for an existing sitcom, should it be in a two-act or three-act format.
Some backstory. For years sitcoms followed the two-act formula. There was a big commercial break in the middle. Then some networks decided it would easier to retain the audience if they sprinkled the commercials throughout. Thus there were two breaks during the body of the show, not one. And thus the three-act format was born (or hatched).

If you’re writing a “spec script” for an existing sit-com go to the nearest mirror, look at yourself up and down, sideways and backwards, and ask, “Does this sit-com which has been on the air 100 years, and is still #1, really need a new comedy writer? Or would I have more chance showing-off my talent by writing something original?”
You’ll have equal chances succeeding either way. But you’ll sleep better and walk taller with the latter. Been there-done-that-sanford.
The way I see it, nothing needs new writing blood more than a smug, smartass old show.
Plus, someone’s got to replace the old staff members whose time served has gotten them big bucks development deals all over town.