"On screen, she was magic. Off screen, she was one of the kindest, sweetest, most caring [women] I've ever known," Mark Hamill says of the original Lois Lane.
The actress most famous for bringing Lois Lane to life on the silver screen was 69 at the time of her death, which took over Twitter Monday morning as news quickly spread.
According to TMZ, Kidder's cause of death is currently unknown, but foul play has been ruled out. Park County Attorney Bruce Becker said that someone called police to report Kidder was unconscious and not breathing in her home. Police responded and found her dead.
Kidder's career took off when she starred opposite Christopher Reeve in the 1978 "Superman" movie as well as the film's three sequels. Despite a very public battle with bipolar disorder, Kidder continued to take on small acting roles in TV shows and movies up until this year. She also had a part in "The Vagina Monologues" on Broadway.
During her struggle with bipolar disorder, Kidder was briefly homeless in 1996. She later became an advocate for mental health awareness.
"On screen, she was magic. Off screen, she was one of the kindest, sweetest, most caring [women] I've ever known," Mark Hammill tweeted. "I'll miss you, [Margot Kidder]. Your legacy will live on forever." Elijah Wood also expressed his sadness on Twitter, simply writing, "Oh no, Margot Kidder."
See how other stars and fans are mourning the loss below:
oh no, Margot Kidder.— Elijah Wood (@elijahwood) May 14, 2018
RIP Margot Kidder— Roseanne Barr (@therealroseanne) May 14, 2018
My Lois Lane has passed away. RIP Margot Kidder. Thank you for my favourite movie ever. pic.twitter.com/dUmxwOUjyi— Mark Millar (@mrmarkmillar) May 14, 2018
Awwww, rest in peace Margot Kidder. Loved you for so much more than being such a feisty Lois Lane. https://t.co/zpEidgX6NT— Meg Cabot (@megcabot) May 14, 2018
RIP Margot Kidder. One of my favorite movies of hers is the original Black Christmas. It introduced some elements that are now genre tropes and she’s fantastic in it.— Kumail Nanjiani (@kumailn) May 14, 2018
#MargotKidder was incredible in the Superman movies. The Lois Lane she created had so much strength, humor and vulnerability that she became as much a part of what made the movie work as the wonderful Chris Reeve, Gene Hackman and others. #ripmargotkidder— Clark Gregg (@clarkgregg) May 14, 2018
Rest In Peace Dear #MargotKidder ❤️ I was such a fan of yours from the first moment I saw you on the screen as Lois Lane in Superman! I will treasure the moment that I met you forever! Sweet dreams Margot🌤— Maureen McCormick (@MoMcCormick7) May 14, 2018
Margot Kidder should be remembered as much for courageously, candidly discussing her battles with mental illness as for any screen role.— David Axelrod (@davidaxelrod) May 14, 2018
There are no Supermen— or women. It is not a character deficiency to acknowledge such struggles and get the help and treatment you need!
RIP to Margot Kidder, who made sure my generation knew just how awesome Lois Lane was. pic.twitter.com/5BU0qDYKrB— Eric Goldman (@TheEricGoldman) May 14, 2018
It was so great to have someone like Margot Kidder's Lois Lane in my life growing up. RIP. pic.twitter.com/rNCXybVCUr— Jill Pantozzi ♿ (@JillPantozzi) May 14, 2018
Like Carrie Fisher, Margot Kidder's human struggle with mental illness and passionate social activism meant as much to me in terms of inspiration and love as her iconic on-screen role.— Joanna Robinson (@jowrotethis) May 14, 2018
Sad to hear of the passing of Margot Kidder. A spark of vivacious life in all of her films. I loved her in cult horrors 'Sisters' and 'Black Christmas'. And of course she remains the best Lois Lane in the magical 'Superman' & 'Superman II'. RIP to a unique screen presence. pic.twitter.com/bQEVv7PSa3— edgarwright (@edgarwright) May 14, 2018
RIP Margot Kidder. An actor who imbued all her roles with grit, strength and smarts. I admired her very much and she’s gone way too soon. I chatted with her a couple of times at conventions. Happy I told her what she meant to us— Barbara Crampton (@barbaracrampton) May 14, 2018
So sorry to hear about the passing of Margot Kidder, a great actress and a tower of strength. 69 is too damn young!— Bill Moseley (@choptopmoseley) May 14, 2018