I recall a story in Road & Track magazine, circa 1976, were the author was reminiscing about a (former) fellow autoworker at a Ford plant, ordering and assembling a one off F-100 under the noses of the plant supervision, during the late 1960s.
He ordered a basic-bare bones truck, and that's how it started when the chassis first hit the assembly line. By the time it reached the end, however, it sported air conditioning, power steering, disc brakes, a deluxe interior, and the Pièce de résistance, a 335 HP 390 cube V8 and HD C6 tranny from a Fairlane GT (both of which were otherwise unavailable on the F-100 pickup, at that time).
According to the story, it made it off the assembly line unnoticed, and all the way to the dealer's lot, where the sales manager noted a few "minor" discrepancies between the truck that had been ordered, and the one that had been delivered to his dealership...oooops!