Players can play against one another through the Nintendo Wi-Fi connection with a tally of their records, or simply play with others with a DS nearby through DS Download Play if they do not have a copy of the game.
The character Ermac actually originated as a glitch from the original Mortal Kombat arcade game. If a player unlocked the secret battle with Reptile, on rare occasions the game would experience a glitch, resulting in Reptile's palette changing from green to reddish orange, and his name text changing to "ER MAC" ("error macro"). After this was discovered by players, the producers decided to officially make "Ermac" a character.