I never saw epic o_o
lol but anyway... 
For Marvel I'd say, we should visit the Ultimate universe and the Mainstream Universe as those two are the most prominent. 
Though if neither are acceptable I'd say maybe the cinematic universe because Why the hell not? XD
Marvel isn't really necessary though. I know I suggested it, but I honestly thought it was one hell of a long shot. 

As for standard disney... 
- Wreck-It Ralph world 
It would be so awesome lol 
And it could so tie into the grid as both are set in virtual worlds. Just a thought. 
- Monster's Inc world
It'd pose big problems. Not only do we need to deal with heartless, but also monsters because the citizens would think the heartless are good and we're bad because we're human (mostly). With the exception of Mike and Sully nobody would really listen to us (most likely). It would be awesome and we'd probably need to be more sneaky and stuff. 

Those are my current best suggestions that aren't already in this and haven't been in KH to my knowledge.