When it comes to The Lord of the Rings, discussion always circles back to the f***ing eagles. In fact, you can't go two minutes without someone pointing out that instead of Frodo and Sam making the treacherous pilgrimage to Mordor, they could have just caught a lift with the eagles, flown over Sauron's armies, avoided Gollum and simply plonked the ring into Mount Doom from afar.
It's become one of the most popular "plot holes" in cinema history - not helped by the creatures also turning up as a deus ex machina in The Hobbit, further drawing attention to their exclusion from the bulk of LOTR's story - but one convincing theory originating from Reddit claims that forgetting to use the eagles to destroy the ring wasn't actually an oversight, but a result of Gandalf's original plan going haywire.
It posits that Gandalf, not only being allies with the creatures but also, you know, having a brain, planned on using their powerful abilities to complete his objective in a safe (okay, safer) way. After he escapes the now-evil Saruman's lair on the back of an eagle and realising he's essentially alone in figuring out a way to dispose of the ring and stop Sauron, he opts to not travel straight to Rivendell and instead goes for a private meeting with his saviours.