In the comments to my Miller-Boyett post, asks about how Full House was re-tooled before it aired. I don't know much about it, but Wikipedia says that the original idea was for the three guys to be comedians. And there was an unaired pilot with a different actor whom Bob Saget was brought in to replace. And I recall reading that there was an even earlier version of the pilot script by different writers (MTM refugees and Who's the Boss? creators Blake Hunter and Martin Cohan) that didn't get used.
Anyway, one thing I forgot to mention about Miller-Boyett shows was that they all had insanely long opening sequences with uplifting theme songs. Once the Laverne and Shirley theme became a hit, no matter how farcical the show was, the song always had to be some huge inspirational thing about standing tall on the wings of the family everywhere you look, because out of the blue the sweet insanity will come to you. But when they re-tooled the show, they'd always go back and shoot new footage for the title sequence and re-tool that as well. Observe:
Angie, season 1:
In season 2, the setting is different and a character has been dropped, so most of the characters are brought back to the location in Philadelphia to shoot outdoor footage -- I guess the theory being that if they change the setting again, they won't have to re-shoot footage of people eating hot dogs outdoors. Also, the first season executive producer is already gone. And the song has been remixed.
Perfect Strangers season 1, when they were working at a crummy job, focuses mostly on how two guys both came to Chicago pursuing a dream and nothing's gonna stand in their way, even if they have to work a crummy job, yada yada.
And then the opening credits everybody remembers, which are almost entirely about how awesome these guys lives are and how successful they are (they get to go to ball games, run around in revolving doors, and just generally live in Chicago the way Ferris Bueller lived for only one day).