Henry Ford was a known prankster. This was a lifelong passion of Ford.
Among the earliest accounts are Ford nailing down a pair of shoes to the floor left by a messy co-worker, blowing sulfur fumes into a sealed room through a knothole in the paneling, and perhaps the most painful- hotwiring a urinal!
One yarn that is seldom told is the broken pocket watch gag. While he repeated this often over the years, perhaps the best account is the one given by Charles Sorensen-
Seems as if Henry Ford showed up at Sorensen's stateroom on the Henry Ford II while on a trip to examine a potential site for a branch assembly plant. During this late night meeting Ford told Sorensen about the plan and instructed him to find a cheap knock off watch similar to the Howard watch that was a prized possession of Frank Klingensmith, at the time one of Ford's top executives. During a stop at port the next day Sorensen went and found a similar watch in a jewelry store and rushed back to the 'yacht' (actually an iron ore carrier, but Ford always referred to it as his yacht) and gave the watch to Ford.
Henry Ford turned the mainspring in the cheap watch to where it would run slow and exchanged watches in Klingensmith's vest while the vest was hanging on a lavatory door. Ford slipped the Howard in his pocket and walked away.
On deck, Ford set the itinerary and instructed everyone to check their watches so they could meet up at a specified time. Klingensmith made the comment that his watch was running slow. Sorensen grabs the watch from Klingensmith and said "well no sense keeping a watch that won't work" and threw it against a wall on the dock, promptly shattering it into pieces. Ford & Sorensen keeping a straight face, while Sorensen said "that was a fool thing for me to do Kling."
Klingensmith was seen scavenging all the pieces he could find while complaining to Sorensen & Ford that the watch was keepsake from his grandfather and could not be replaced.
3 weeks later the Howard watch was found in one of Klingensmith's other vests, having been delivered to Klingensmith's house by Henry Ford personally. He gave the watch to his wife who put it in the vest pocket.
Henry Ford had actually started tinkering with watches before cars & even in his later years would carry an eyepiece and watchmaker's tools in his pocket just on the in case someone had a watch that needed attention.