Text (UH): 1/1. ; {1}: This card's name becomes the name of your choice. Play this ability anywhere, anytime.
This card's flavor text looks like an ability but it isn't. "{1}: This card's flavor text becomes the flavor text of your choice. (This ability doesn't work because it's flavor text, not rules text (but neither does this reminder text, so you figure it out).)" [Card Text]
This card has no name. The underscores are used to make it clear that there is no name, but the name has no underscores in it. [Unhinged FAQ 2004/11/15]
You can only choose a name that already exists in Magic. You cannot make up a completely new name. [Unhinged FAQ 2004/11/15]
While the rules officially say you can't, it's more fun to let you play the ability to change the flavor text if you want to, but you can only change it to some flavor text that already exists in the game. [Unhinged FAQ 2004/11/15]
All tournament formats have banned cards from Unhinged.