Yes, the 'rubbernecker sightseers' were a relatively common metaphor when this thing was first written. It refers to the drivers who pass an accident and all turn to get the best view of the accident in the other lane, and stop paying attention to what's in front of them.
Edit: And mittens are gloves, technically, the types that don't have fingers only a thumb, but collect all the fingers together in a single pocket, but in this case I think that mittens refers more to the hands within them, and refers to the sort of people that see a button and instinctively press it without understanding what they do.
Edit: And spitzensparken refers to spits and sparks. Poppencorken is a kind of explosion, so it refers to the moment when all of the valves fail in a row, shower the room with little fragments of glass and start shorting out.