A friend made the illuminating suggestion that E 18 is essentially episode 1 of season 4. Now I know a new season hasn't been announced, but if you look at that episode in this context it makes a lot of sense. It practically all takes place in this alternate dimension with a new set of rules (i.e. cooper's car switch, the dead body on Carrie's couch, Richard and Diane switch, etc)

Also, i'm not sure if this has been discussed yet, but I really think that Mr. C and Cooper are literally the same person. We see hints of Mr. C in Coop after crossing into "Judy", especially that scene in the cowboy diner. I think Mr. C is what ends up happening to Coop after aeons of trying to resolve his karmic cycle of rescuing Laura Palmer. Perhaps he becomes Mr. C because of how maddening these reality loops become. He becomes hardened and dark because he cannot progress past a certain level. Anyone feel me?