Few would disagree that “More Cowbell†was one of Saturday Night Live’s most memorable sketches throughout its run — and that also includes Jimmy Fallon, even though he couldn’t stop breaking the fourth wall as the Blue Oyster Cult’s drummer during the latter half of the sketch to save his life. (Perhaps one of the symptoms of too much cowbell.) Still, after all of these years, he has a good sense of humor about it and its Reaper-ness. “That was one of my first sketches ever and I was like, Don’t screw it up,†he explained to Andy Cohen this week. “I started laughing and I screwed up my line and then that became my thing. I was the guy who laughed during sketches.†Some love it, some hate it, but at least Fallon seems chill with his giggles.