Blake Lively, David Boreanaz, Ed Westwick, Kim Cattrall, Kenan Thompson, Melissa Joan Hart and more shared tributes to Trachtenberg.

Actor Melissa Gilbert, who acted alongside Trachtenberg in A Holiday for Love, honored the late star on Instagram by sharing a picture of the two from the project. “Oh Michy…and we lived so close to one another…..my heart aches for your family and all those who loved you so…” she wrote.

Michelle Trachtenberg's co-stars and fellow celebrities are speaking out after the "Gossip Girl" and "Harriet the Spy" star was found dead Wednesday.