The Simpsons is making TV history on Sunday, April 29 when the Fox animated series airs its 636th episode, beating Gunsmoke's record of scripted episodes. However, Gunsmoke and Law & Order are both still tied for the longest-running US primetime live-action series with 20 seasons produced.

In "Forgive and Regret," the 636th episode of The Simpsons, Grandpa Simpson (Dan Castellaneta) makes a deathbed confession to Homer (also Castellaneta), but after recovering, Grandpa realizes the issue is not one easily reconcilable.

"We certainly didn't expect to last this long," The Simpsons creator Matt Groening told USA Today. "When we started, we didn't even know if the Fox network was going to last, much less our own show. Fox was an experiment, and they allowed us to do pretty much whatever we wanted."