'Fuller House' cast mourns death of beloved colleague, Cosmo the golden retriever

"Fuller House" cast members are mourning the loss of a member of their TV family, Cosmo the golden retriever.

Cosmo, who was 4, died after complications from surgery. The show's Twitter account announced the news Monday, accompanied by photos of the dog, who started on the Netflix comedy as a pup.

"We're sad to share that the Fullers' faithful dog Cosmo, who grew up on our set, passed away after complications from surgery," the tweet said of the dog, who answered by the same name on the show and in real life. "There will never be another quite like our boy. We'll miss him forever."

Netflix released the first nine episodes of the fifth and final season of "Fuller House," a sequel to popular ABC sitcom "Full House" (1987-1995), earlier this month. The second half of the season, which has completed filming, will premiere in 2020.

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Cosmo had appeared in other shows, including "Suits" and "The Middle." according to a March interview with his trainer, Denise Sanders. The dog died a couple of weeks before the end of production, according to a touching Instagram tribute video by Elias Harger, 12, who plays Max, one of the Fuller children.

Cast members chimed in on social media Monday, sharing their love and sense of loss for their cute colleague. Candace Cameron Bure, who played child D.J. Tanner on "Full House" and portrays mom D.J. Tanner-Fuller on "Fuller House," referenced Comet, the family dog on the original series.

"Our sweet boy Cosmo is now running around in doggie heaven. I imagine he's playing with Comet right now," she tweeted. "Cosmo has been in Fuller House since the start and we are heartbroken that he passed away during surgery complications. You'll be so missed love bug."

Jodie Sweetin, who has played Stephanie Tanner on both "House" shows, also shared loving sentiments. 

"As you may have heard, our beloved Cosmo has passed away. He had gone in for surgery and suffered complications. Our little Cosmo was always such a good boy and our hearts are (broken)," she finished, with a broken-heart emoji closing the tweet.

Elias Harger, 12, who plays D.J.'s son, Max, is seen with Cosmo in pictures shared in tweets by the show and Cameron Bure. He paid tribute to his friend on Instagram, noting their first "Fuller" appearance together in the fifth episode of Season 1.

He sweetly remembers how they grew up together on the show and the sad moment when Cameron Bure, Sweetin and co-star Andrea Barber sat down with him to share the news of Cosmo's death. 

"Two weeks before the end of @fullerhouse, I lost my buddy. I made this video to honor @cosmofullerhouse." Another broken-heart emoji.

A Cosmo Instagram account thanks cast members, fans and others for their condolences. "Thank you to everyone for all the kind words, condolences and prayers for Cosmo. To say that Cosmo was an incredible dog does not even begin to capture how truly magnificent he was."