Executive Meddling: They tried. According to Candice Bergen at the TV Land Awards, executives were a little concerned that a 40-something woman recently back from rehab might not be sympathetic, and asked if she could be a 20- or 30-something woman recently back from a spa vacation. Diane English protested, and it was eventually averted.
Highly unlikely, given the poor sales for the season 1 set and the high cost of licensing the vintage Motown music used on the show.
The Other Darrin: Up until and including the episode where Jim and Doris separated, Doris was played by Janet Carroll. In the final season, she was played by Concetta Tomei. The difference was notable, to say the least.