To fantasy fans, it's a plot hole to end all plot holes: If the three hobbits from the Lord of the Rings trilogy are smart enough to get to Mordor on foot, why aren't they smart enough to fly there on giant eagles, saving them time and toil? I mean, none of them are idiots. (Well, Frodo and Merry aren't idiots.)
Well, wouldn't you know it: There's a fan theory for that, and here it is. After you see it, you may never see Gandalf -- or a hobbit, for that matter --in the same way again.