Witherspoon's Instagram post featured behind-the-scenes pics from the production of the film, including a pic of her with Elle's beloved dog, Bruiser, a shot of herself roller skating, and snaps with cast members.
"Omigod you guys ….#LegallyBlonde premiered 20 years ago TODAY! Time flies when you're busy using legal jargon in your every day life," Witherspoon wrote, referencing some of Elle's most iconic lines. "But truly... playing Elle Woods was the role of a lifetime and I'm so honored to have been a part of sharing her story with you all."
"Every meme, graduation cap, musical number, Halloween costume and bend & snap has brought me so much JOY over these past two decades!" she continued. "I wonder... what will Elle do next?"
Witherspoon also celebrated the milestone on her Instagram Story, calling it "a very exciting day."
"Playing this character literally changed my life. It changed my whole career," Witherspoon said. "But it also completely opened me up to so many people in the world who come up to me every week or every month, literally, and say, 'Elle Woods inspired me to go to law school. Elle Woods made me believe in myself. I played Elle Woods in the school play!'"
"So I really feel like I share Elle Woods with every single person that made this film, who I love so dearly, but also with all of you," she continued. "I just love sharing this character with you guys."
Blair, who played Elle's nemesis-turned-friend Vivian Kensington, similarly celebrated, sharing throwback snaps on Instagram, along with a heartfelt caption.
"This was a time before cameras on phones. I walked around with a tiny vintage camera but never remembered to take many," she wrote. "I was too busy hanging out with Matt Davis talking in my trailer, or watching Reese work. I made lifetime friends. Fell on my face impersonating Billy Elliot. Right after the group shot. Where I am standing on my toes. Trying to be taller. While Reese was inside… on set working. Making Elle Woods. I love you all."
On her Instagram Story, Blair shared Witherspoon's post and wrote that she had "the time of my life" making the flick.
Larter, who starred in the flick as Brooke Taylor Windham, an accused murderer that Elle, her classmates and her law professor work to defend, reminisced on Instagram, too.
"20 years, my friends! There is something very special about being part of a movie that brings people laughter and joy!" Larter wrote alongside pics of her in the movie. "It has shown the test of time, and I love the smile I see on everyone’s face when they think of Brooke Wyndham! And, come on, the Dior wardrobe."
"The cast was stellar, lead by the force of nature @reesewitherspoon," she continued. "Tell me your favorite parts of Legally Blonde and if it inspired you to believe in yourself at all costs!"
When ET spoke to Coolidge earlier this month, the actress, who played Elle's manicurist-turned-friend Paulette, offered up ideas about how the film's 20-year anniversary should be celebrated.
"It's going to be like a giant jet ride to somewhere really far away and I think there must be a party in some big castle or something. At least that's what I will be hoping for," she told ET. "All I had to do was age 20 years and I am at the anniversary. I didn’t even have to work for this. 20 years went by and then you get credit for being alive and making it to 20. You see, all of the other girls when we made Legally Blonde were like 11... My journey was much harder."
As for the upcoming third flick, Coolidge said, "I have not seen the script. I am told Mindy Kaling and Reese Witherspoon are talking about it and I hear it is going to be finished soon. I heard it is close but I haven’t seen it, I really haven’t."
Watch the video below for more on Legally Blonde 3.