Nine-time Emmy Award-winning writer and producer Sam Simon passed away on Sunday evening at the age of 59, two years after he was diagnosed with terminal colon cancer. Simon was best known for co-creating The Simpsons, but became a notable philanthropist in his later years by donating his vast fortune to a number of pet charities and starting his own foundation which rescues hungry and stray dogs.

Simon started his brief yet prestigious career writing for the animated Fat Albert and the Cosby Kids in 1979 and then acting as showrunner on the sitcom Taxi at the young age of 23. He went on to write for and produce Cheers and The Drew Carey Show and write the 1991 film The Super. The Stanford graduate developed The Simpsons with Matt Groening and producer James L. Brooks while the trio was working on The Tracey Ullman Show; they first introduced audiences to Bart and his family during animated sketches shown before and after commercials for the show. In a statement released Monday regarding his co-creator’s passing, Groening fondly recalled Simon’s “phenomenal talents, sharp intelligence, and sly sense of humor.”

One of Simon’s most significant contributions to The Simpsons was hiring elite writers such as George Meyer, John Swartzwelder, Mike Reiss, Jon Vitti and Conan O’Brien.

“I remember Sam coming into the room, and me pitching to him and initially being really intimidated,” said O’Brien in a 2007 interview with Vanity Fair. “He’s hilarious. It was fun to try and make him laugh. I remember that about Sam. If I could make Sam laugh, I was excited.”

Simon left the show in 1993 after four seasons, but since The Simpsons is the longest-running primetime series in American history, his deal tied to home video sales helped him remain a millionaire for the rest of his life. He recently returned to the entertainment industry to be a consultant on the Charlie Sheen series Anger Management, but a majority of his time was focused on his philanthropy. His Malibu-based Sam Simon Foundation was reportedly worth nearly $23 million as of 2011, and he frequently contributed to pet charities such as PETA, which named its Norfolk, Va., headquarters The Sam Simon Center, and the Sea Shepherd Conservation Society, which named one of the four ships in its fleet of vessels the M/Y Simon.

“He was a genius and a great humanitarian in ways public and private,” said Simpsons executive producer Al Jean in a statement. “I personally owe him more than can be repaid, but I will do my best to help every animal I can in his memory.”