1.Mandy Moore got into the holiday spirit by posting this headshot of herself in a Santa outfit.
2.Janet Jackson shared her fourth grade class picture.
3.Joseph Gordon-Levitt posted this photo of himself and Zooey Deschanel hanging out at Sundance in 2001.
4.Amy Sedaris shared this photo of herself hanging out with her friends Paul Dinello and Stephen Colbert in the late '80s (?).
5.Will Arnett posted this screen-cap from Arrested Development.
6.Elton John remembered when John Lennon joined him onstage at Madison Square Garden in 1974.
7.Susan Sarandon shared this behind-the-scenes photo from The Witches of Eastwick.
8.Orlando Bloom posted this photo from when he did a photo shoot for Teen Vogue in the '00s.
9.Backstreet Boys' AJ McLean shared a very late '90s photo of himself.
10.Antonio Banderas posted this photo of when he and Cameron Diaz promoted Shrek the Third in Rome in 2007.
11.And finally, Andrea Barber (aka Kimmy Gibbler) shared this photo of herself, along with her Full House co-stars Jodie Sweetin, Candace Cameron, and Mary-Kate and Ashley Olsen, at the Hollywood Christmas Parade in the early '90s.