I "think" that dark matter observations are the effect of interference between different Everett branches. The smaller is a volume space, the less possible states it has, so gravity in the center of a galaxy would be less that in the borders. The borders of the galaxy are more entropic because more different states are possible, ergo the stars there experience interference with more Everett universes. Gravity being so weak, it would only show its effects in other branches at huge scales. In this "theory", it seems that dark matter effects would be less visible the further away in space (time) we look. No idea if that's the case.
Again, I have no idea what I'm talking about, so this is just for fun.