The 35-year-old SNL star recalled the awkward bathroom incident she had with the 50-year-old actress and singer during Thursday's episode of The Tonight Show Starring Jimmy Fallon.
It all started when McKinnon decided to use the bathroom before heading to the show's host dinner. But when she entered the communal restroom, she found Lopez touching up her makeup.
"I walked in and I was like, 'Hey, how are ya?'" she told Jimmy Fallon. "I went into a stall and sat down and I was like, 'Oh my God, no! Now, I have to pee in front of Jennifer Lopez. This is awful.'"
Not wanting Lopez to hear her pee, McKinnon decided to "wait it out."
"And then, like, three minutes went by, and I still hadn't made a sound," she said. "And there we were: stand-off."