When Jamie Lee Curtis found out that Lindsay Lohan, who was going to be playing her daughter, had starred in The Parent Trap (1998), she asked, "Which twin did she play?", unaware that Lohan had performed both roles.
A member of the band Orgy instructed Jamie Lee Curtis on how to play the guitar. In the concert sequence, that is actually Curtis playing during the solo.
Kelly Osbourne originally auditioned as Anna (not as Anna's best friend) and was offered the part but decided to back out. Later, she said people told her it was the biggest mistake she'd ever made, due to the success of the movie.
The snapshots in the opening credits are actually photos of Jamie Lee Curtis and her daughter Annie Guest.
Producer Andrew Gunn said he initially hoped Jodie Foster, who played the daughter in the original film, Freaky Friday (1976), would be game to play the mother in the remake. Foster declined, in part because of concerns that the casting stunt would overshadow the movie's overall merit.
Lizzie McGuire: Those Freaky McGuires (2002), an installment of Lizzie McGuire (2001) (also produced by Disney), is considered a fourth version of Mary Rodgers' story. "McGuire" star Hilary Duff and Lindsay Lohan had a rivalry during this period, and apparently, Duff, losing out on this role, demanded that her show get "Freaky" for one installment.
Mark Harmon and Jamie Lee Curtis repeat their roles as lovers eight years later in the ninth season of NCIS (2003), as Special Agent Leroy Jethro Gibbs and Dr. Samantha Ryan.
Michelle Trachtenberg was cast as Anna, but had to back out, due to her contractual obligations to Buffy the Vampire Slayer (1997).
The cover of Tess Coleman's book, "Through the Looking Glass", is the same cover as the original Freaky Friday novel written by Mary Rodgers.
Annette Bening was originally slated to play Tess Coleman. She backed out shortly before filming, and was replaced by Jamie Lee Curtis. Sigourney Weaver was also considered.
The "S" and "Y" on the Sony television in the teacher's lounge is blacked out, leaving "ON" on the front of the set.
Chad Michael Murry (Jake) and Julie Gonzalo (Stacy) later worked together on A Cinderella Story (2004) in similar roles. Murray was again cast as the main character's love interest, while Gonzalo was again cast as the main character's rival.
The guitar that Jamie Lee Curtis plays offstage during the show at the House of Blues is an Ernie Ball/MusicMan Steve Lukather (Toto) Signature Model.
As an homage to Jamie Lee Curtis's mother Janet Leigh, known for her performance in Psycho (1960), a character named Mr. Bates is present in the film. This is a nod to the character of Norman Bates in Psycho (1960).
Lindsay Lohan has starred in a few movies that involve some sort of "swapping". In this movie, her character swaps bodies with their mother. In Just My Luck (2006), her character swaps fortune and luck with a man. In The Parent Trap (1998), she plays both twin sisters, who swap lives, and pretend to be one another.
There are various F.o.N. posters in the garage. F.o.N. is the band in which Danny Rubin plays.
Marc McClure: Annabelle's love interest (Boris) in Disney's original version of Freaky Friday (1976) as Boris the delivery man.