"May the mother who left their kid near the third base line, come back he's on the field".
It happened during yesterday's White Sox/Orioles game and he was quickly scooped up by White Sox outfielder Dayan Viciedo who handed him over to a security guard.
The boy was safely returned to his guardian and both were ejected from the game:
Update: Here is a better video of the kid running onto the field from Off The Bench:
(Courtesy of CSN Chicago)