They say Helen of Troy had a face that could launch a thousand ships, well, the Living MacGuffin has a similar ability to launch a thousand quests in search of them. The Living MacGuffin isn't an inanimate MacGuffin made flesh (that's MacGuffin Girl), or a kidnapped Damsel in Distress or President's Daughter; what the Living MacGuffin is is a character who is quite free, in little to no danger, desperately sought after and out of the hero's reach. She may be a heart wrenchingly beautiful princess whose hand can only be won with miraculous feats, a long lost (or left) parent, sibling, close friend or Love Interest, or some variation of The Chosen One who is needed for some greater purpose. (But remember, if that person serves another purpose later in the story, they're Chekhov's Gunman.)