some had a brim, and even a propeller. The point was always that they make you look inexperienced and foolish, and were a kind of mild hazing as they were often burned as students finished their freshman year.
WikipediaA whoopee cap is a style of headwear popular among youths in the mid 20th century in the United States. It was often made from a man's felt fedora hat with the brim trimmed with a scalloped cut and turned up. In the 1920s and 1930s, such caps usually indicated the wearer was a mechanic. It is also...
https://en.wikipedia.org/wiki/Whoopee_cap