Something I hadn't noticed before is that Mike appears as early as 40 minutes into season 1, episode 1, standing in front of Coop and Sheriff Truman as they take the escalator to the morgue. Then, as they examine Laura's body the lights flicker off and on with an electrical clicking sound. Someone needs to make a movie of the parts of season 1 and 2 that are relevant to season 3.
Just watched some of the relatively minor middle episodes of S2 (from 17 onwards) and there’s a lot of stuff relevant to S3. The major’s disappearance, the very straightforward explanation of the White and Black Lodges from Hawk. And Catherine talks about being saved by a guardian angel after the fire - initially that sounded like bullshit but it’s more plausible after the various appearances and disappearances in S3.