It was only the ninth time James was blocked in 1,850 career dunk attempts over his career, per ESPN Stats & Info.
Allen expressed pride in being one of only eight different players to block a James dunk, according to ESPN.com's Ian Begley: "That's a helluva list to be on. He's an amazing player. I got the chance to do it, so I'm on the list forever now."
Despite the rarity, the Los Angeles Lakers star was able to shrug off the moment after the game.
"He's in his twenties, I'm in my thirties. It takes me a little longer to get warmed up, but that's fine," James said, per Anthony Puccio of NetsDaily. "When you're a shot blocker, I'm sure you can get a block. It happens. It's probably all over social media, so that's cool."
People were definitely talking about the block on Twitter and Instagram throughout the night, helping Allen potentially become more of a household name during his breakout second season in the NBA.
Meanwhile, James has had quite a few of his own viral moments, so he can probably let one go the other way.