Here we see a group of people participating in an old fad known as “Brake Dancing”.
It involved groups of people dressing up in costumes (in this case, as a baseball team), locating a station wagon (the “Brake”), and fancifully gyrating around it.
Although the trend started in Europe and was briefly popular among american hipsters, it failed to catch on due to a distinct lack of station wagons to fancifully gyrate around.