Other mistake: When Will confronts his mother about not wanting to move back to Philadelphia, she mentions she can't afford to send him to an out of state school. However, in season 2 it's already been established that Uncle Phil is Will's legal guardian, and he's a resident of California. Will's mother has it backwards. Going to school in Pennsylvania would be an out of state school and staying in California would be in state.
Continuity mistake: Will's hat from his school uniform keeps changing from a snap back to a strap-back in each scene he's wearing it. (00:10:00 - 00:13:00)
Answer: Yes. It's very true. Janet quit at the end of the third season because she claims that Will acted horribly, bullied cast and crew on the set and got her fired for no reason. Alfonso Ribeiro however has called her "cuckoo" and stated that her claims were baseless. He also stated that she was very difficult to work with on set. Even James Avery agreed and often had to remind her that the show was called "The Fresh Prince of Bel-Air" and not "Philip and Vivian of Bel-Air."