A Princess Crown is an object that most princesses wear, also known as a tiara. Princess Bubblegum's crown is golden and has a blue gemstone on top. Flame Princess' crown is a big ruby. Most crowns are different in many ways. The Gemstone in Princess Bubblegum's crown is used to block out mind controlling powers such as those from The Lich. In "The Lich," Finn and Jake go around Ooo stealing all the gemstones from Princess' crowns for "Billy," but there were many princesses that they missed, even though in the episode the plot explained that they had all of the gemstones they needed. As far as actual crowns go, Hot Dog Princess and Bee Princess' are the only crowns that are proper crowns.