I've had both happen more than once to me, though I wouldn't consider my channel in the same league as yours.
Some channels that were mainly doing "G Major" videos have adopted my "Horror Version" label. What's funny is that "G Major" was reasonably popular long before I got involved, and mine is just a variation of it. I've had people re-upload my videos, sometimes crediting me, sometimes just copying my entire description into theirs.
I've had channels worried that their favorite videos of mine would get taken down and upload them to their channel to archive it, explaining that in their description.
When my channel was terminated for 3 days, at least 4 channels made videos showing their upset reaction to it. When I got it restored, one made a video showing their reaction to that.
YouTube's a funny place.