The sad news was announced by the Netflix series on its official Twitter account on Monday, December 16, with the page writing, "We're sad to share that the Fullers' faithful dog Cosmo, who grew up on our set, passed away after complications from surgery. There will never be another quite like our boy. We'll miss him forever."
Following the news, Candace, who plays D.J. Tanner-Fuller in the programme, wrote on Instagram, "Our sweet boy Cosmo is now running around in doggie heaven. I imagine he's playing with Comet (the dog from the original 'Full House' series) right now. 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 stars as Stephanie Tanner in Fuller House, added her own tribute to the canine alongside a picture of Cosmo, writing, "Our little Cosmo was always such a good boy and our hearts are (broken heart emoji). Say hello to Comet for me, buddy."
Actor Elias Harger who plays young Max in the programme, shared the most scenes with Cosmo, and the 12-year-old shared a video chronicling the dog's life on his Instagram page.
"It was sometimes hard to get Cosmo to pay attention and stay on his mark and I had to be careful not to distract him during the scene," he said in the video. "But he grew into a seasoned actor. In fact, we both learned to control our energy on set. We might have acted together, but our friendship was no act."
"I used to worry he would forget me when we were off work for months at a time, but he never did. Cosmo would come back to work at the beginning of each season and melt into a wiggling mess of dog kisses, wagging tails and brown eyes burning with joy."