Chapter Two: Trick or Treat, Freak - S2-E2
Continuity mistake: In episode 1, during Will's appointment discussing his episode, the doctor said "how did you feel, when you saw the storm?" Will then replies "Frozen." Doctor says "Heart racing?" Will: "Just frozen." Doctor: "Frozen? Cold frozen? Frozen to the touch?" In this episode When the doctor watches the tape of his conversation with Will from the previous episode the dialogue is different. On the tape, after Will says "frozen" the doctor then says "actually frozen cold?" Which he didn't say in the previous episode. And his actual lines from the first episode are missing. (00:25:15)
Chapter Two: Trick or Treat, Freak - S2-E2
Continuity mistake: When Steve is trying to keep Nancy from drinking more alcoholic punch, he pulls on her cup. She pulls away and the punch spills all over her blouse. The spill stain changes significantly from shot to shot. The stains in the second shot are no longer there in the third shot. (00:42:22)
Chapter Two: Trick or Treat, Freak - S2-E2
Continuity mistake: As Hopper and El sit down to breakfast after she has surprised him as a ghost, he tells her he will bring candy home etc. When the camera is on Hopper, El is leaning on the table, but when the camera is facing her, she is leaning back.
Chapter Three: The Pollywog - S2-E3
Continuity mistake: When Dart is found in the bathroom cubicle by Will, he drops his walkie talkie when he runs away, but shortly after when his friends arrive the walkie talkie is gone.
Continuity mistake: When Mike and Will are discussing Will's visions near the start of the episode, the sweat stain on the front of Will's shirt disappears and reappears between shots. (00:01:30)
Answer: The body was fake, made by the scientists at Hawkins Lab in an attempt to cover up his disappearance and the existence of the Upside Down.