So the fumes from the kerosene heaters which kept my fingers functioning while replacing some vacuum lines must have gotten to my 2000 Chevy Blazer as it started hallucinating that A. It was a car that could do 100 miles per hour and B. That it was doing said speed in my garage.
Happily, after disconnecting and reconnection the battery again, the speedometer has returned to its normal condition. I was however, able to freak out some of my more cautious friends by sending them this picture despite the fact that the car is idling and is visibly in park.
Oh, the joys of car ownership.