I don't remember exactly when it happened but I recall before the last Harry Potter book was published in 2006? I got hooked on the series and powered through all the books in a week. I finished and, much like fans of GRRM books I couldn't wait for the conclusion. I scoured the internet looking for details about the final book and lo and behold I found an advanced copy of the final book.
I downloaded this pdf file to my computer and opened it up. It was close to three hundred pages and it had the right font so it looked legit.
I read the WHOLE thing before I realized it was purely a work of surprisingly detailed and faithful fan-fiction. I can't recall any details but suffice to say that was the day I learned not to trust anything written on the internet.
P.S. I couldn't help but include this because it gives me chills