How 'The Simpsons' Paid Tribute to Stephen Hawking

The Simpsons paid tribute to one of its greatest guest stars, Stephen Hawking, Sunday.

The famed theoretical physicist died aged 76 on March 14.

Sunday's episode of the animated comedy featured a card in memory of Hawking. The still is from the 1999 episode, "They Saved Lisa's Brain!," which marked Hawking's first guest appearance alongside Homer, Marge, Bart, Lisa and Maggie.

Simpsons executive producer Matt Selman shared the graphic on his Twitter page:

— Matt Selman (@mattselman) March 19, 2018

As well as being one of the most famous scientists in the world, Hawking was a big fan of The Simpsons and appeared in four episodes of the show between 1999 and 2010.

His first appearance saw him fly into Springfield to save Lisa Simpson. His last appearance, which aired in September 2010, featured him singing alongside Lisa after she joined a school glee club.

Selman recently told The A.V. Club website that Hawking would also visit table reads and hang out with the show's cast and crew.

"One year, or a couple of years, he was just hanging out—he would come to table reads and be there hanging out. Like, 'There's Matt Groening. There's Dan Castellaneta. There's… Stephen Hawking. At the read. Just enjoying our world,'" said the producer.

"I think he saw that there's a certain absurdity in everything, like in trying to figure out the laws of the universe or silly Simpsons stories. I think he shared that absurdist sense of humor. Our show is sort of about trying to find meaning in a chaotic world—I think he related to that as well."

Hawking also made appearances in numerous episodes of CBS comedy The Big Bang Theory.

The show's producers paid tribute to him on Twitter last week, sharing a picture of Hawking and the cast—including Jim Parsons, Johnny Galecki and Kaley Cuoco—on set.

In loving memory of Stephen Hawking. It was an honor to have him on The #BigBangTheory. Thank you for inspiring us and the world.

— The Big Bang Theory (@bigbangtheory) March 14, 2018

"In loving memory of Stephen Hawking. It was an honor to have him on The #BigBangTheory. Thank you for inspiring us and the world," the tweet said.