17-year old Adam Lamberg as Gordo; because he hit puberty late, he is actually able to pass as a 12-year old pretty convincingly in the pilot, and he managed to remain shorter than Lizzie and Miranda all the way through to the end.
Animated Lizzie: Wow, Miranda's officially in love with acting. Maybe when she's thirty years old, she can play a teenager on Dawson's Creek.
Defictionalization: In one episode, Lizzie was inspired to spend more time with her mother after reading a novel titled The Orchids and Gumbo Poker Club for a school assignment. Disney later published an actual novel with that title, with notes from Lizzie included in the margins.
Yani Gellman (Canadian/Australian) as Paolo (Italian) in The Movie. Also in the movie, Hilary Duff herself plays Isabella, with the result that Isabella loses her Italian accent whenever she's singing.
To be fair, Hilary's sister Haylie seems to provide Isabella's singing voice, but she is also not Italian.
What Could Have Been: They seemed to be building up to a romance between Larry and Miranda before the latter left the show. The storyline where he hooks up with a minor recurring character was most likely originally for her. Also, Sara Paxton was also considered for the role of Lizzie.
There were plans to spin off a "Lizzie in high school" sitcom onto ABC, but never got to be produced, due to Hilary Duff leaving after the show's completion.
A pilot for an unaired spinoff series called "What's Stevie Thinking?" was allegedly shot (or at least written), concerning the adventures of Miranda's sister Stevie. Stevie was to be played by a very young Selena Gomez.
Towards the show's end, there was a contest for three girls to have animated versions of themselves to have a cameo with the animated Lizzie. The show ended before this could have happened.
After the 9/11 terrorist attack, the clocks in Lizzie's school are set at 9:11 for the episode directly after it.