The 50-year-old actor and his The Gentlemen co-star, Hugh Grant, are on The Tonight Show Starring Jimmy Fallon on Friday, and play a game of "True Confessions." In the game, which ET exclusively debuts a first look, each gentleman is asked to tell a story from an envelope while the other men guess whether he is telling the truth.
While all their stories were pretty wild, McConaughey's tale was downright unbelievable. "I once ate peyote in a cage with a mountain lion," he proclaims.
After McConaughey explains to Grant that peyote is a small, spineless cactus that when ingested can cause hallucinations, he goes into how he managed to find himself in this situation about 14 years ago.
The How to Lose a Guy in 10 Days star says that the "easy part" was getting in the cage with a mountain lion. Though he doesn't answer whether the animal also took peyote, he does note, "I will say this, four hours later the mountain lion was cuddled up with me and purring."
"It was one of the more thrilling escapades of my life actually," he adds. "This was just me and the mountain lion."
As crazy as the story sounds, both Fallon and Grant believe McConaughey, who confirms this did in fact happen to him.
Watch the video to see if Fallon actually did get "hit by a car at full speed and survived," and if Grant "had a compulsion to stick apple peels" up his nose as a child.
"His father's 91, my mother's 88," McConaughey said of playing matchmaker to his mom, Mary Kathlene McCabe. "Yeah, why not? Next week, they're supposed to meet, and we probably won't see them for the rest of the night."
Grant jokingly added that their parents' meeting would be "red hot." But the sons will have to wait and see if Mary and Grant's dad, James, will hit it off. In the meantime, McConaughey might have a future in matchmaking. His only requirement is "they have to be over 85."
As for their movie, The Gentlemen, it seems only fitting that Flaviar would team up with the film to release a 23-year-old Speyside Scotch. Deer, Bear & Moose The Gentlemen by Flaviar was bottled in 1996 and is priced at $220.
Meanwhile, The Gentlemen arrives in theaters on Jan. 24.