If you caught The Tonight Show With Jimmy Fallon last night, you were lucky enough to hear Denis Leary share a story about the time he saw Rod Stewart's penis.

It all dates back to 2008, when Leary was hosting CBS' Fashion Rocks award show. Stewart and old pal Ronnie Wood were performing the classic "Maggie May" that night. Just before the performance, Stewart borrowed Leary's backstage room to make a quick wardrobe change, at which point the actor and comedian was unexpectedly confronted with an up-close view of Stewart's famous ass.

Then, as Leary told Fallon, the naked singer turned around, giving Leary a clear view of his penis. "I'm just lasered in on it," he recalled. "You don't look at other guys' junk, but I thought the ass didn't qualify as junk. So I thought, 'I'm gonna stare at your Rock and Roll Hall of Fame ass.'" Then Stewart turned around.

The rest of Leary's story involves Stewart and a glass of wine, a stolen peek at Stewart's Little Rod and a once-in-a-lifetime Freudian slip as Leary introduced Stewart onstage as "Cock Stewart." You can hear the entire story in the above video.

The second season of Leary's FX show, Sex&Drugs&Rock&Roll, premiered last month. Stewart is all set to hit Las Vegas with his Rod Stewart: The Hits tour for nine performances starting on Aug. 3. The show plays a few more U.S. dates before heading overseas for a bunch of European dates that will keep Stewart on the road for the rest of the year. Tickets are now available.

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