1. John Stamos shared this photo of him and Lori Loughlin hanging out together in 1982.
2. Janet Jackson posted this photo from the time she did a Dorothy Dandridge-themed photoshoot in the '90s.
3. Tegan and Sara shared this childhood photo of themselves dressed as Oscar the Grouch and Big Bird in honor of Halloween.
4. Orlando Bloom shared a behind-the-scenes photo from The Hobbit in honor of Peter Jackson's birthday.
5. Ian McKellen reminisced about The Lord of the Rings by posting this behind-the-scenes pic.
#TBT 2000, A sunny day in New Zealand, filming "The Lord of The Rings"
6. Amy Schumer remembered when she appeared as Gretel in a stage production of the Sound of Music in 1986.
7. Jensen Ackles shared this sweet #TBT pic of him and his wife, Danneel Harris.
#tbt Our first vacation together...and even then you were rockin the headband. ❤️ u @DanneelHarris
8. Zach Braff remembered his iconic photobomb.
#tbt Photobomb level 10.
9. Wesley Snipes shared this photo of himself from the early '90s.
Pose like someone is trying to take your food 👌🏿#tbt
10. Kylie posted this VERY '80s photo of herself.
11. Shania Twain shared this photo of herself in 1997, in celebration of the 20th anniversary of her blockbuster album Come on Over.
12. And finally, Christina Aguilera celebrated the 15th anniversary of her iconic album, Stripped, by sharing some photos from the linear notes.
CORRECTION
The photo Orlando Bloom posted is actually from the set of The Hobbit. A previous version of this post listed the wrong film series.