Ed Boon from Midway and Jimmy Palmiotti of DC Comics announced four new additions to the Mortal Kombat Vs. DC Universe roster at Comic-Con today, Green Lantern and The Joker on the DC side, with Jax and Kitana on the MK side. That makes around ten total characters we know about with plenty more to be released over the coming months.
Boon also announced that an MK vs. DC comic book would included in the limited edition of the game, illustrated by John Tobias, co-creator of the Mortal Kombat series. The game's final boss and a the remaining line-up of fighters was promised to be announced over the next few months. They also showed off a new environment, Superman's fortress of solitude; which looks really awesome. We got our hands on the game at E3 '08 and walked away very impressed with what the guys at Midway and DC Comics are coming up with. Stay tuned for more information (including a hands-on report) on MK vs. DC as it is released, right here on PlanetXbox360.

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UPDATE - IGN receives image of the Joker character - "Why So Serious?" - Click Here. . .