If there is one thing that immediately convinced me that Garabandal is absolutely demonic, it is the fact that the children were filmed walking backwards. This is typical for the devil, doing things backwards (singing, talking, walking, …) in mockery. This walking backwards during ecstasies can be clearly seen in one of the many videos at the 4:01 mark: “… with their eyes fixed upwards, they walked forwards and backwards throughout the village…”
After seeing this one publicly documented fact, the case for me was closed. Garabandal is undoubtedly demonic. God does not perform a circus for the whole village, and He certainly does not cause people to walk backwards, like the devil is wont to do. Full stop, case closed.
Unfortunately, some Catholics have this insatiable hunger for anything supernatural, for visions, messages and prophecies, and they will happily switch off their brain in pursuit of more visions and messages from “heaven”. For those people who need more than one proof of the demonic nature of Garabandal, the following link contains so much evidence, that is it is completely beyond me how any sane person, after reading all this, can still go on believing in such nonsense as Garabandal.
Please note, the author [RIP] was not a Traditional Catholic and I obviously do not endorse everything he said. Still, there are enough excellent arguments and proofs that are worth your time to read.