Now, I know that this is off topic stuff but the off topic sections have been sealed for years and I know you guys will actually read this.
Here is an Adventure Time theory I've concocted Which I've dubbed as "The Crown Theory".
Here goes:(You probably need some background in Adventure Time to understand this)Long ago the newly formed Lich was sweeping across Europe in the form of the Black Plague.
A king living during this time (Billy maybe?) finds out what is causing this and defeats the Lich, sealing his power inside his crown and banishing the Lich to a life of roaming the land as a shapeless shadow. He finally is able to gather enough strength to possess a human, only to find that he doesn't have enough power to wage his eternal war against life.
For centuries he gathers power which he stores in his Well of Power, until he finds the location of the crown of which his old power was stored. He quickly finds out that because of a certain gem inside the crown which makes him unable to operate it without a considerable amount of power and a living host to wear it.
He coaxes a man by the name of Simon to buy it and soon after activates it, causing the Mushroom War. This doesn't destroy all life though and before the Lich can try again Billy defeats him and sends him to his amber prison.
He is free now, though, and is gathering strength. Though his Well doesn't hold enough power, he is close, and soon he shall be able to once again activate the Crown (currently resting on The Ice Kings head) and destroy life, once and for all.
That was a lot of typing.