Sam Simon, one of the executive producers on The Simpsons, hasn't worked on the show since 1993 despite being credited on every single episode.

Simon was instrumental in the creation of The Simpsons more than two decades ago. Time called the TV show the best in the 20th century. He hasn’t been a producer on the TV series in over 15 years, but is still credited in each episode. 

It is a tribute and thanks to him for how he helped lay the foundation of the show and hired many of its long time writers. Simon had a way of making the cartoon characters three dimensional. 

Simon still makes money from the show, too. Today, though, Simon’s main focus is on his foundation named the Sam Simon Foundation. The foundation rescues dogs from the pound and trains them to be companions to the deaf. He dabbles in a lot of things, though, too.

He had a poker show on the Playboy Channel and enjoys collecting art. He was a manager for the boxer Lamon Brewster and took him to the Heavyweight Championships and then retired. 

(Source)