Conan has a recurring sketch on his show called "Alex Trebek has gone insane," where he splices together clips from various Jeopardy! episodes to make Trebek sound crazy.
Conan opened the segment by showing one of the (admittedly hilarious) clips before Trebek joined him on stage and took his revenge.
The 73-year-old Jeopardy! host came out and wagged his finger at Conan before he expressed concern for the late night star. "I'm worried about you," Trebek said. "I've been listening to some of your monologues lately and I'm concerned. I think you are starting to lose it."
Trebek then showed a video of his own, which featured clips of Conan spliced together to not make any sense. "Miami police announced they're releasing a video of Justin Bieber urinating in his jail cell. Yeah, it was the first time toddlers were able to plant their crack pipes right there in the top of another dog's butt," Conan declared in the video. The clip only got crazier from there.
Trebek ended his appearance with a raunchy spliced sentence to serve as a warning to Conan. "The ex-president of Ukraine, James Van Der Beek, often massages weasels..." Trebek began.
Conan O'Brien will host the 2014 MTV Movie Awards on Sunday, April 13.