Her music, mainly pop, includes the albums J.Lo and On The 6, a reference to the subway line she used to take growing up in Soundview.

Although the franchise is extremely popular, it is not without critics. Some cite a lack of interactivity (overuse of Full Motion Video), rigid and often linear story structure and unoriginality. With the exception of Final Fantasy VII, the games that appeared in CD form on the Sony PlayStation and PlayStation 2 platforms that are scenario-written by Kazushige Nojima, are especially attacked by critics within the video game community. Nintendo's Legend of Zelda, Konami's Suikoden, Rockstar's Grand Theft Auto and Square Enix's Dragon Quest franchises are strong competitors of Final Fantasy. Much of the Final Fantasy fanbase is believed to have conservative attitudes, especially since the time of Final Fantasy VII, and many critics have such attitudes.

Duff's first movie role was in Human Nature, an independent US/French coproduction released in 2001. She starred in the television movie Cadet Kelly with Christy Carlson Romano and Gary Cole. Her first hit movie was Agent Cody Banks with Frankie Muniz in 2003. Duff then reprised the role of Lizzie McGuire in The Lizzie McGuire Movie, which was her first million-dollar movie role. Her final role of 2003 was costarring in the Disney film Cheaper by the Dozen with Steve Martin and Bonnie Hunt. Her success as a singer led to her being rated as number 96 in the Forbes Top 100 Celebrity List.