In a profile of Fallon penned for the TIME 100, Timberlake reveals that during the groom’s impromptu, emotional speech to Biel following last October’s nuptials, his late-night talk show host pal decided to mix things up.

“Picture this: I’m in the heart of an impromptu speech at my wedding reception in front of 150 guests, pouring it out to my lovely new bride. You could hear a pin drop,” writes Timberlake, setting the scene.

He continues, “I paused for just a moment in between thoughts. And then there was Jimmy, shouting a joke from his seat, sparking an improv between the two of us that went on for a good five or 10 minutes and had all our guests roaring with laughter.”

“Interrupting the groom’s speech at the wedding reception? Cracking jokes when your buddy is looking desperately for the words to say that he hopes his wife will remember forever? It turned into a moment that everyone there will remember forever,” adds the “Suit & Tie” singer.

Timberlake concludes, “Anyone else would have bombed on that stage. And then I would have kicked their a**. But this was Jimmy Fallon. He just can’t help himself.”