Plot summary
When the Banks family attends a seance so Hilary can contact her dead ex-fiancé Trevor, Scorpius, the spiritualist ( Glenn Shadix ) gets so frustrated with Will's mockery and skepticism that he curses the family with a hex that brings them all bad luck: Uncle Phil is put out of business because of assumed evidence that he was taking bribes and faces jail time, Ashley breaks an ankle just before her tennis match, Carlton's hair gets bleached as a result of his Macaulay Culkin Halloween costume, Geoffrey gets deported, and Jazz and Hilary plan to get married.
Will must convince the psychic to break the curse but when he returns, he realizes the man who cursed the Banks looks like a nerd, his real name is Ralph Scorpius, and he has none of what he had when he placed the curse. Will then wakes up from this dream but the day starts just like it did like an endless timeloop.
Credits
Adapted from Wikipedia contributors, The Fresh Prince of Bel-Air season 4. HTML formatting and reference markers removed.