"Reggie" says the home run trot was started by Harmon Killebrew. He said that Killebrew used to hit such high fly balls that there was no point in his running hard because if they were not homers, then they were going to get caught.
I can think of two instances of player over over-exuberance that I saw in high school. One was, when our eventual state championship football team was ahead of the second best team in the state, 50-0, a cornerback made an interception and nearly had a public orgasm on the field. The other was in a JV basketball game, when a guy most of us regarded as a jerk made the first of two free throws with a four or five point lead and under ten seconds remaining, and he had to be figuratively dragged back to the line to attempt the second shot. This whole "celebration" thing is definitely a post baby boom pathology