The first trailer for Bel-Air, the 2022 reboot of The Fresh Prince of Bel-Air, reveals a very different depiction of Uncle Phil and Carlton. With any reboot, it makes sense for the characters and story to go through changes from how they were originally depicted. Bel-Air appears to be going down the same path, and there are a few possible reasons for why that could be.
Bel-Air is based on the 2019 fan film of the same name. Both the show and the fan film follow the original premise of the show where a young Will Smith is sent to live with his aunt and uncle in Bel-Air after getting into a fight in Philadelphia. Compared to the original show, however, the 2022 reboot Bel-Air is treating the situation with far more seriousness and gravitas, with the first trailer even revealing that Will was sent to jail for pulling out a gun and that one of the guys he got into a fight with is looking to kill him.
Bel-Air is very obviously going for a more serious tone than The Fresh Prince of Bel-Air, and this is further reflected in its portrayals of Uncle Phil and Carlton. Uncle Phil, as played by Adrian Holmes, is far skinnier than James Avery was, and his interactions with Will seem to lack a lot of the lightheartedness that they had in the original series. Carlton, meanwhile, is the same overachiever that he was in the original series, but now he’s actually succeeding in his endeavors and appears to be popular while Will is starting off as an outcast.
With Bel-Air's Uncle Phil, an actor with a skinnier build was likely cast because a lot of jokes about his character in the original series revolved around his weight. While those types of jokes were common in the 90s, general opinions about body positivity have changed a lot since then, and those types of jokes could be viewed as insensitive and fatphobic today, so it’s probably better for them to do what they can to avoid it. In regards to his personality, as previously mentioned, Will’s circumstances are being handled far more seriously than in the original show, with him living with the Banks being treated like he’s in the witness protection program, to the point that only a few people know the truth of why he’s there. As such, whenever Bel-Air's Will does something stupid or gets in trouble, it’s not just that he’s wasting his potential, he’s also wasting the only chance he has of staying alive, so it makes sense for their dynamic to be more serious.
With Carlton, going along with the serious tone, it probably wouldn’t work to have the character be as outright goofy as he was in the original series. Not only that, but making Carlton the popular one and Will the social outcast maintains their dynamic of a cool person and a lovable loser—the only difference being a turnaround of who’s who, so it provides a familiar story beat, but with a new twist to go along with the change in tone. The trailer also shows that Carlton doesn’t know the truth of why Will’s there and is suspicious of him, so that suspicion could be why Bel-Air's Carlton is acting so serious around Will, and once they get closer or Carlton learns the truth, he might start acting closer to how he did in the original series.
The biggest reason for the changes, of course, could be because of how iconic the original characters were. Bel-Air will undoubtedly be heavily compared and contrasted to The Fresh Prince of Bel-Air, so trying to stay as close to the original as possible could just make people want to go back to the original instead of sticking with the new show. The changes to Uncle Phil and Carlton were likely made with that in mind and done in the hopes of providing a new experience unique enough to keep people invested in the long run. The Fresh Prince reboot is due to release in February 2022, so how successful they were at doing so will be seen then.