Michelle Tanner became a main character in season two of Full House, after being a recurring character during the first season.
Michelle was the youngest Tanner daughter, played by twins Mary-Kate and Ashley Olsen. Because she was an infant when the series began, the producers initially treated her as a recurring role rather than placing the twins in the main opening-credit cast.
Her role expanded as the series found its audience and Michelle grew older. From season two through season eight, the character was part of the principal cast and increasingly received storylines built around her speech, friendships, school life, and family adventures.
A common mix-up is confusing Michelle's first appearance with her promotion to the main cast: she appeared in the 1987 pilot and season one, but season two is when she officially joined the main cast.