1. Reese Witherspoon posted this photo from when George Clooney photobombed her and Kristen Wiig at the Met Gala.
2. Eva Mendes also reminisced about the Met Gala, and the time she took Rashida Jones as her date.
3. Dolly Parton was serving looks in her #TBT.
4. Tegan and Sara shared a cute and very '80s #TBT.
5. Iman shared a photo of herself looking gorgeous alongside her late husband, David Bowie, at the CFDA Fashion Awards in 2007.
6. Kylie shared this glam photo of herself from 1991.
7. Speaking of glam, Joan Collins took us back to her days on Dynasty:
8. Luke Evans remembered when he played Dracula.
9. Mindy Kaling shared a behind-the-scenes photo from Season 1 of the Mindy Project.
10. Josh Gad shared a pic from his blonde ambition days.
This might be the most absurd #tbt post ever. This was me going through my Slim Shady phase. #whydidnobodystopme
11. Joseph Gordon-Levitt shared this cast photo from his 2013 film, Don Jon.
#DonJon family portrait w/ @TonyDanza, @brielarson and Glenne Headly.. #TBT
12. Madonna posted this photo of herself from the early '80s in response to the news that Universal is making a movie based on her life.
13. And finally, Ellen DeGeneres posted this photo in celebration of the 20th anniversary of her coming out publicly.
#TBT to 20 years ago. Don't miss tomorrow's show. @Oprah