Alex Trebek made a hilarious appearance on this '90s sci-fi show. (What is 'The X-Files'?)

“Supernatural” comes to an end Thursday after 15 seasons, six more than the original run of one of its progenitors and influences, “The X-Files.” (The less said about those two recent revival seasons, the better.)

Sam and Dean were definitely cooler than Mulder and Scully, but their show couldn't boast a guest star as cool as Alex Trebek.

“Jose Chung's From Outer Space” was a self-referential 1996 X-file anchored by a hilarious performance from Charles Nelson Reilly — a cool guest star in his own right, but no match for Trebek, the “Jeopardy!” host who died Sunday at age 80 after his public struggle with pancreatic cancer. I won't spoil the nature of Trebek's appearance in the episode, a wild re-creation of a Mulder-and-Scully case from Reilly's titular author.

It was a groundbreaking third-season episode for the sci-fi/horror show that paved the way for future funny episodes. Stream it on Hulu.

When Alex met Cliff

Trebek played himself in a beloved episode of “Cheers,” available to stream from Hulu, CBS All Access and Peacock. The Season 8 episode “What Is ... Cliff Clavin?” follows John Ratzenberger's would-be know-it-all as he tries to become a “Jeopardy!” champion. His response to the Final Jeopardy clue — in the category of Movies, “Archibald Leach, Bernard Schwartz and Lucille LeSueur” — is one of the biggest laughs in sitcom history.

Final Jeopardy

And don't forget a great big-screen appearance from Trebek and “Jeopardy!” in the 1992 comedy “White Men Can't Jump.” The main action focuses on Wesley Snipes and Woody Harrelson as street ball hustlers, but a subplot sees Rosie Perez's Gloria achieve her lifelong goal of competing on the game show. It's available for digital rental and sale.

• Sean Stangland is a Daily Herald assistant news editor who has never passed the “Jeopardy!” test.