The 1920′s equivalent to like… planking or T-posing was “pole-sitting”, in which people would climb to the top of flag poles and sit there. For days.
There were public contests and fierce competitions for world-records to see how long you could remain sitting on the top of a pole. A guy named Bill Penfield set the world record in 1930 by sitting on a pole for nearly 52 days, only coming down when threatened by a thunderstorm.
Dance Marathons also began in the 1920′s. They were a lot more exciting than sitting on a pole, but just as fucked up. The point was to dance for as long as possible, until you dropped to the ground unconscious - people would tie themselves to their partners. There were usually compelling monetary rewards, which became a lot more tantalizing in the 1930′s. Plenty of people died from exhaustion.