Many years ago, while out in service, I encountered a young university student who held me to task over 1914, and made me face the specific implications if the prophecy were to fail and be changed. It wasn't an Aha at the time, but many years later, it became a retroactive aha.
The big one for me was when the hidden picture stories were floating around, back in the early 80's. Everyone talked about them, and admitted to seeing them. My uncle, who was a former missionary, stated that he had heard from his bethel contacts that someone in the art department had been disfellowshipped for it. Well, as time went on, I wondered how the society would handle it - I mean, how could Satan infiltrate that deep into the word of God? Just as I had decided that they were going to ignore it, an article came out which off-handedly mentioned that the pictures were all just a rumor.
Now, my Aha was not the pictures. It was the reaction. When the Society stated that the pictures did not exist, everyone clammed up. No one would talk about it. My uncle, with his inside information was the first person to denounce those who thought the pictures were real. If the society says black is white, then by God, black is white.
This was the first real crack in the wall that I saw. Once I actually started to look, I realized that the wall was nothing but cracks.