Hello, everyone. Just thought I'd drop in and share some of my own theories on the Man Who Speaks In Hands. First off, I've watched Swanky Box's video on the good doctor several times, so if you wish to see it for yourselves, here it is:

Now, moving onto my theory. In the Genocide Route of Undertale, Sans mentions that reports showed anaomlies in the Space-Time continuum, with timelines starting, stopping, jumping left, right, up and down and all around. However, it is also widely believed that Dr. Gaster was spread all over time and space after his accident. Therefore, I find it very possible that Dr. Gaster may actually be the cause of the anomalies Sans was talking about.

And well, that's my theory in a nutshell. What do you guys think?

I think it's possible, but remember... Gaster isn't the only one that can do this...

Chara is a possible candidate for messing with the timelines... even if they don't possess Frisk...