17 Again star Sterling Knight is remembering the time he spent with his late movie sister, Michelle Trachtenberg, in the wake of her sudden death.
“Some quick thoughts. Thanks to everyone for the bday wishes, I ended up having emergency gallbladder removal surgery (would not recommend) but I’m healing up nicely. With the timing of that, and the passing of Michelle, who was so unbelievably kind to me, it made me think,” Knight, 36, wrote via Instagram on Friday, March 7. “Tomorrow is not guaranteed and it’s important to tell those close to you that you love them and appreciate them as often as possible.”
He added, “Michelle was generous, kind and beyond helpful to me as I navigated my first big movie. I had grown up watching her (as we all did) and she always had time for me if I had questions or was struggling.”
Knight and Trachtenberg, who died in February at the age of 39, played siblings Alex and Maggie in 2009’s 17 Again. The two former child stars portrayed the children of Matthew Perry and Leslie Mann’s respective characters. (Perry died at age 54 in October 2023.)
“I’ll never forget hanging out with Matthew and Michelle in her trailer, for hours, talking about life and work, lessons and wisdom they had picked up,” Knight said on Friday. “Bit of a combo update/gratitude post, but thanks again to everyone and I’m feeling much better. Miss you Michelle. Love y’all.”
Us Weekly confirmed Trachtenberg’s death last month.
“It is with great sadness to confirm that Michelle Trachtenberg has passed away,” her rep told Us in a statement on February 26. “The family requests privacy for their loss. There are no further details at this time.”

Michelle Trachtenberg, Matthew Perry, Sterling Knight New Line/courtesy Everett Collection
Trachtenberg — best known for roles in Harriet the Spy, Ice Princess, Gossip Girl and Buffy the Vampire Slayer — is survived by her parents, her sister and her boyfriend. (Trachtenberg started dating talent agent Jay Cohen in 2020.)
A cause of death has been ruled as “undetermined” after the actress’ family objected to an autopsy. Trachtenberg had initially been found unconscious by her mother, Lana, inside her New York City apartment.
“On Wednesday, February 26, 2025, at approximately 0801 hours, police responded to a 911 call of an aided individual at 1 Columbus Place, within the confines of the Midtown North Precinct,’” local law enforcement officers said in a statement at the time. “Upon arrival, officers observed a 39-year-old female unconscious and unresponsive. EMS responded to the location and pronounced the victim deceased. Criminality is not suspected.”