Dog Rescue Advocate Isabel Klee Is Saying Goodbye To Soul Pet Simon: His Sweetest Moments

Bestselling author and animal rescue advocate Isabel Klee shared the heartbreaking news on Instagram that her beloved dog Simon would soon cross the rainbow bridge in July 2026. The mixed-breed rescue, who lived with epilepsy and was diagnosed with cancer toward the end of his life, has been a central part of Klee's storytelling and lauded by Klee for helping foster pets feel safe and at ease while in their home. His adventures are chronicled on the Instagram page named Simon Sits, where Klee tearfully gave the solemn update about Simon's condition while talking about how loved and missed he will be.

To celebrate Simon's extraordinary life in the spotlight, Cuteness has compiled some of his sweetest moments since puppyhood to showcase his gentle personality and the lasting impact he has had. In true form, Simon leaves behind a legacy measured not necessarily in years, but in every life he helped change over the course of his time on Earth.

There's no better place to start our sweetest moments journey than when Simon was just a fluffball of a puppy, especially when he was dapperly dressed up like in this adorable pic. (And, really, who doesn't like dogs all dressed up and ready to paw-ty?) His owner, Brooklyn-based Klee, had recently taken him in as a rescue from the South Korean meat trade, not knowing that he had complex medical issues until she had already fallen desperately in love with him. Luckily, he found the right home to live his best life for as long as possible.

File under: Little pup, big city. Yes, Simon lived his life in the Big Apple — Brooklyn, to be exact — looking right at home even as a tiny puppy on a big BK stoop, as this one photo perfectly captures. He lived his life in the bustling borough as Klee's resident helper for dozens of foster dogs that passed through their apartment over the years. According to Klee, he had a natural instinct for helping nervous newcomers adjust to city life before finding families of their own.

In a post titled "I have proof that my dog is the best foster brother in the world," Simon's dog mom shared all "the proof" she needed: slide after slide of Simon cuddling up and playing with numerous foster dogs that came in and out of their house. From small dog breeds to much older dogs and everything in between, Simon seemingly made friends with everyone. And, really, who couldn't love that face and personality? "He is such a good boy 👏," noted one person in the comments.

Chronicled on Instagram, Simon always had a knack for helping even the most fearful foster dogs open up in the Klee home. A perfect example was with this sweet, memorable boy named Tiki, who one day came out of his shell and started playing with Simon to Klee's delight. In the comments on the Instagram video featuring Tiki, one person made sure to say, "I'm amazed with how much you can do to improve the quality of life for so many," referencing one of the ways to help animal shelters without adopting or giving money. 

Whether dressed up or just sitting in front of a pumpkin patch, Simon was clearly photogenic. That personality-plus is probably what helped him make so many friends, whether with humans or other animals. Cute, funny, happy, excited, just chillin' ... Klee captured all the big and small moments in Simon's life as any obsessed pet parent would do; we were just lucky enough to be a part of their journey as outsiders. Now, his legacy will live on through every photographed doggy smile and real-life rescued friend.

From rescue to whole heart, anyone who has ever adopted a pet knows how quickly you can become invested and obsessed. For Isabel Klee, Simon changed her world and her life, propelling her onto the New York Times Best Sellers list in the process with "Dogs, Boys, and Other Things I've Cried About," begging the question: who rescued who? For Simon, he lived a life full of happiness and tender loving care that helped him thrive and help others despite complex medical issues. May his loving legacy live on and help other animals in need.