The only explanation I can think of for this goofy criminal is that some writer noticed the popularity of polka dots at the time (remember this was the era of the song "Itsy-Bitsy Teenie-Weenie Yellow Polka Dot Bikini") and decided to make a criminal with that theme. PD Man is another one of those crooks where you can't help thinking he could make a fortune just selling his inventions.
