Thanks@TeacherOfPain
Checkmating using the KING!!

I guess it's counterintuitive though. Why move your king and rook for checkmate when you should just be able to slide the rook over instead? You have to have a clear rank anyway for the rook and king to move, so I guess it would have to be used to get the rook on the OTHER SIDE of the king to mate. I'll try to find an example.

I ran through this, and castling was the only way to win at this time.
This is assuming both players were dumb, and then white finally got a clue.
The video posted above two comments ago is a better example for those who want to watch it.

Have to wonder what Black was thinking on his previous move. If his Queen checks White's King, Kc7 or e7 results in the same mate. So, must move something else, what did he move?
Moving one of his pawns on his previous move would not to allow such an obvious back rank mate. But what about Ra7? This forces White's King to stay on the 8th rank and that back rank checkmate is gone. Now it gets very interesting . . .
Yeah using the King to checkmate by moving him or castling has to be one of the coolest ways to checkmate, and it is very rare so it makes it the more better.
I don't think I have checkmated by just moving the King from as far as I can remember, so it seems like a good achievement as most people are not avaliable to do that!
Nice @SmartyKnight