This is a funny little insight into the lunacy of sports fandom. Much like with the players, there are unwritten rules of decorum for fans and one of those rules is that you must throw an opposing team's home run back onto the field if you catch it. People will straight-up yell at you if you don't. They made a whole movie where this very act leads to a Major League career for a teenager. But catching a home run is also pretty cool. You caught a statistic, and it's a game-used souvenir that you didn't have to buy off some charlatan memorabilia peddler. This, until now, has always been a quandary.
Amazing. This guy either brought a ball with him, got his hands on a batting practice home run, or maybe even bought one at the game and had it stashed in his pocket. After he catches Chris Johnson's home run he deftly and unnecessarily spins around, distracting everyone from what he's really doing. As he spins, he pulls out the dummy ball from his pocket, and launches it back into center field, all while the real home run ball is stowed safely in his glove.
It may not be the best ball trick we've seen at a game, but it's pretty good for an adult.