We're not scientists but kids develop facial recognition when they're like, 2, right? So how is it that no one else worried about this woman claiming to be Aunt Viv? That is not your aunt! Get out of the house, imposter!
According to Will Smith, the O.G. Mrs. Banks, Hubert-Whiten, whose character much more career-oriented and outspoken, was fired from the show because she had bad attitude toward working with the then-rising star, so producers replaced her in season four with Reid, who played a more subdued, homemaker version of Aunt Viv.