That was just a slide showing the new characters in the 6-pack. The "surprise" part was the Red Hood/Joker that had not been prevoiusly announced.
Thanks for the info Julius. I guess it was hard to understand from just looking at the slide. Still don't see why they chose to phrase it "3 pack surprise". Did they mean the red hood/joker was almost like getting 2 characters in one? The word 3-pack doesn't make a whole lot of sense to me.
The point is we're getting Grodd, so I guess that is all that matters.