Alex Trebek: 5 Memorable Moments on 'Jeopardy!'

Alex Trebek has hosted "Jeopardy!" since 1984.

Longtime “Jeopardy!” host Alex Trebek announced Wednesday that he has been diagnosed with stage 4 pancreatic cancer at 78 years old. 

Trebek, who has hosted the long-running syndicated game show since 1984, has had many memorable moments on set throughout the years. 

In 2001, after 18 seasons hosting “Jeopardy!” Trebek shaved his mustache, which he'd had for 30 years. He rocked a fake mustache on April Fool’s Day in 2008 to prank his viewers but did grow an official ‘stache in 2014 for the 31st season of the show. It only lasted a month. 

During a 2005 Tournament of Champions special, the host opened his very serious game show in a not-so-serious way by walking onto the set without pants as a way to relieve some of the tension among the contestants. 

Trebek, known for his very serious disposition, once took a crack at busting a rhyme on set during a 2015 episode, where he rapped a whole category. The “It’s a Rap” category featured clues to songs by the Beastie Boys, Dr. Dre, Grandmaster Flash, Notorious B.I.G. and Public Enemy.

The audience got chuckles when he would spit out the lines “I’m nuthin’ but a G thang / Never let me slip ’cause if I slip then I’m slippin’” from Dr. Dre’s “Ain’t Nothin’ but a G Thang.” 

In 2014, he entered the Guinness Book of World Records for Most Gameshow Episodes Hosted by the Same Presenter, overtaking Bob Barker’s run on “The Price Is Right.”

Trebek also likes to have fun on his set, as clearly indicated by some of his antics including a 2006 episode in which he danced to a clue’s answer, which was “What is a strobe light?” 

In announcing the news Wednesday, Trebek struck a reassuring note in his video message to fans posted on YouTube. 

"Normally the prognosis for this is not very encouraging, but I am going to fight this and keep working," Trebek vowed. 

He added that he had received the news just this week. 

Patrick Swayze, Steve Jobs and Luciano Pavarotti have all died of the disease. In 2009, Supreme Court Justice Ruth Bader Ginsburg was diagnosed with pancreatic cancer; she later beat it.