I had a nice uncle in NYC I visited from time to time. I took the PRR clocker up to Penn station, while getting off one day I noticed the GG1 that was pulling the train I was on uncoupled from the train and took off....hhmmmm.. I asked one of the RR guys why was the engine taken off and he said, we change motors with the NH. I said when will the other engine come for the train which he replied any minute.
After a few minutes I was rewarded to see a New Haven EP-5 Jet back up and couple to the train. wow how great is this. yet another reason to go see my uncle and catch a ball game.