That's wild! What do you mean they were requesting it one character at a time? The URL itself? If so,how do you know that? Do you also own urls in that "character space" leading up to your URL?
My guess is that each frame of the video was OCR'd for text, so as the author typed a URL in one character at a time it was producing unique substrings on-screen and the youtube bot dutifully tried to fetch each of those unique substrings
That seemed like the gist of it. I wasn't surprised that it was OCR'ing text, but I was floored that it recognized a URL and started firing off requests.
