I've been thinking lately about how they went with MU instead of MI. (which I'm fine with, by the way.)
Mostly, I've been thinking of the playable characters they went with, and I noticed something:
Isn't it weird Sulley doesn't wear his MU jacket? Or Mike doesn't wear his MU hat? Or Randy doesn't wear his glasses?
My theory is that Avalanche designed them like this to make them resemble their MI selves, where they didn't wear these items.
I'm probably wrong, just my theory.
Also, in a Toy Box demo, the music from when Sulley is watching the garbage get turned into a crate is playing in the background.