In the first episode of the second season of The Fresh Prince of Bel-Air, we can see an almost completely redesigned set when compared to the first season.
S01E01 - The Fresh Prince Project (1990)
Still from episode
S02E01 - Did The Earth Move For You? (1991)
Still from episode
Father Phillip Banks (actor James Avery) even mentions the changes during the episode and speaks out to his wife Vivian Banks (actress Janet Hubert-Whitten).
Vivian Banks: [walking downstairs] I'm Ready.
Phillip Banks: Ah, finally. What took you so long?
Vivian Banks: Oh I just spent an hour chasing my outfit on the new rotating dressrack.
Phillip Banks: Why didn't you set the variable speed adjustment?
Vivian Banks: Phillip, these gadgets are making my life miserable.
Phillip Banks: Well honey, you're the one who said we should redecorate.
Vivian Banks: Well yeah! I said we should keep up with the Joneses, honey, not the Jetsons!
IMDb Quotes, Did The Earth Move For You? (1991)
They mention that it was done to keep up with their neighbours, but was there any productional reason (e.g. better camera angles, more light) for this change in set? Did the producers give any reason for these changes?