Michelle Trachtenberg Dead at 39: Rosie O'Donnell, Kim Cattrall and More Stars Who Paid Tribute to the Actress

After Michelle Trachtenberg's death on February 26, her former costars and other Hollywood celebrities took to social media to honor the late actress.

Alyson Hannigan Denisof, who worked with Trachtenberg on Buffy the Vampire Slayer, shared a carousel of photos on Instagram alongside the caption, "I am deeply saddened by the news of Michelle's passing. She brought a loving energy to the set of Buffy. My thoughts are with Michelle's family and friends."

"She was electricity. You knew when she entered a room because the vibration changed. Everything she did, she did 200%," Blake Lively said of Trachtenberg in a heartfelt post.

The It Ends With Us star added, "She laughed the fullest at someone's joke, she faced authority head-on when she felt something was wrong, she cared deeply about her work, she was proud to be a part of this community and industry as painful as it could be sometimes."

Gossip Girl alum Chace Crawford wrote on Instagram, "Michelle was one of a kind. I remember her coming on set for the first time and just absolutely owning it. She was a force of nature and just so so unapologetically funny and magnetic.. remembering those years with a big smile. Just a terrible loss. Love you."

Buffy the Vampire Slayer star Clare Kramer paid tribute to the late actress on Instagram, uploading a photoset featuring Trachtenberg.

"Peace out little one.✌️🧿⚡️💔 A talented & kind soul gone way too soon!💧You’re free to fly now… 🕊️," she wrote in the caption.

Danny Tamberelli, who worked with Trachtenberg on The Adventures of Pete & Pete, celebrated her life in a heartfelt Instagram post.

"We grew up learning how to make people laugh together. More importantly, we learned to make each other laugh and pull pranks on everyone," he wrote. "We were doing improv when it was still called playing pretend to get laughs. She was a master of the clothespin game, tagging any and everyone she could."

Tamberelli also recalled the time Trachtenberg got upset when he played his bass on the set of the series, as he would not hang out with her during lunchtime. She reportedly "hid the cable so I couldn't play through the amp."

He continued mourning the late star, writing, "I got the message. She was a bright light, firecracker and caring person who spent a lot of time and effort advocating for people who needed a louder voice. Michelle was someone to look up to in this business and to the general world at large. She will be missed. All my love, sympathy and compassion to Lana, Irene and the rest of her family and friends."

Ed Westwick remembered Trachtenberg's legacy by sharing a photo of his Gossip Girl costar on his Instagram Story.

He added the text, "So sad to hear of the passing of @michelletrachtenberg sending prayers 🙏🤍."

As Trachtenberg's family and friends started navigating the dark moment in their lives, J. August Richards offered support while also mourning the late celebrity.

"My heart goes out to her family and loved ones. What a beautiful spirit who left an amazing legacy… Rest In Peace, dear one," he wrote on Instagram.

Gossip Girl creators Josh Schwartz and Stephanie Savage addressed Trachtenberg's death in a statement to NBC News, which read, "We are deeply saddened by the news of Michelle's passing. Michelle was so funny, kind, and talented."

The pair continued, "Her portrayal of Georgina Sparks was an iconic fan favorite, and grew from a one season villain to a beloved character who returned over the course of six seasons. She was a delight to have on set and will be deeply missed. Our thoughts are with her family."

Kelly Rutherford paid homage to her late Gossip Girl costar by sharing a throwback photo with a dove and white hearts emojis in an Instagram post.

Saturday Night Live star Kenan Thompson expressed his grief on Instagram, writing, "Our first Nick movie star has departed us!! She was my friend and now she rests!! 🙏🏾 Check on your people!!!"

In an Instagram post, Kevin Zegers said Trachtenberg's death "is a loss."

"Michelle was tough and a force. Just a kid, so sad," he wrote alongside a throwback snap.

Kim Cattrall, who appeared in Ice Princess, marked the passing of "sweet Michelle" in an Instagram post.

"Oh Michy…and we lived so close to one another…..my heart aches for your family and all those who loved you so… @michelletrachtenberg #ripsweetgirl," Melissa Gilbert captioned an Instagram post.

Trachtenberg's Clarissa Explains It All costar Melissa Joan Hart said she is "heartbroken to hear of the passing" of the actress.

"So young, so talented and so sweet!" she shared alongside a clip from the sitcom. "I think this was about 1992 and the episode was an idea I had about babysitting a total nightmare. But Michelle was nothing like her character and even this young, we got along wonderfully."

Rosie O'Donnell, who starred alongside Trachtenberg in Harriet the Spy, claimed the late actress "struggled" before her death.

"I wish could have helped," she said in a statement to Us Weekly, expressing her heartbreak.

Trachtenberg's ex-boyfriend Shawn Ashmore honored her memory in an Instagram tribute post.

"She was an incredible person and I will always remember the years we spent together fondly. She was loving, quirky and would never pass up a [Law & Order: SVU] marathon:) … This is an incredible loss!" he wrote.