Nicky is the baby cousin introduced in season 3 of The Fresh Prince of Bel-Air. He is Philip and Vivian Banks's youngest child and Will's cousin.
Nicky's arrival became part of the show's family storyline late in the third season, when Vivian's pregnancy was incorporated into the series. The character was introduced as a newborn, expanding the Banks household beyond Hilary, Carlton, and Ashley.
A common mix-up comes from the show's unusual aging change. Nicky was portrayed as an infant in seasons 3 and 4, but Ross Bagley later played him as a much older preschool-age child. The abrupt change was acknowledged humorously on screen, but it did not change the character's identity or family relationship.
Nicky is sometimes remembered mainly through Bagley's later performance, even though several babies portrayed him before Bagley joined the cast. He remained part of the Banks family through the series finale, when Philip, Vivian, and Nicky moved to New York.