Doraemon: Nobita and the Galaxy Super-express have the Planet of Cowboys as one of the adventure-themed worlds, where it's main attraction is called "Gunsmoke City". Tourists can partake in the shooting contest, where they duel against robot outlaws using non-lethal firearms.
When Law & Order: Special Victims Unit surpassed Gunsmoke as the longest-running dramatic television series, it acknowledged the event in the opening scene of the episode that broke the record. The SVU episode begins in a bar where the patrons are watching a Gunsmoke episode.
When The Simpsons surpassed Gunsmoke as the longest running scripted television series, it naturally acknowledge it.
With "Treehouse of Horror XXVII", the show becomes the second longest running scripted primetime series after Gunsmoke (with 635 episodes). This is acknowledged by one of the joke credits, which reads "You're next, Gunsmoke".
At the end of "Lisa Gets the Blues", the family discusses how with the following episode they pass Gunsmoke as the longest running TV show. When Bart asks about the radio episodes, Homer stuffs a beignet in his mouth.
"Forgive and Regret" is the episode that surpasses Gunsmoke's record. This is commemorated with a special opening sequence featuring a showdown between Marshall Dillon and Maggie.
Hank Hill is revealed to be a fan of the show in Harlottown, though it never occurred to him what Miss Kitty did for a living. When Peggy points out that it was staring at him in the face the whole time, Hank feels so dirty.
Peggy: Come on. They had all those rooms upstairs, she didn't charge enough for drinks. Hank: Oh, not Miss Kitty...
