How would you like to be 21 years old and a minor league baseball player? Let's add the fact that you are called up yesterday to the big leagues by your boss, the Florida Marlins. You don't start the game but sit on the bench. You are happy to be there. Then you are called into the game as a pinch hitter with the bases loaded (the Marlins are far, far behind so its not the perfect fantasy). That's what happened to Jeremy Hermida.
Anyway, you guessed it, in his first major league at bat he hits a grand slam.
That hasn't happened since 1898.