I remember implementing the flags for this bit in the PPUMASK register in my NES emulator, but never actually integrated it into the graphics rendering.
I always wondered if I would ever need to come back to it…
It is quite an exaggeration to call a grayscale bit in some register a “secret game boy mode”. I would’ve expected something more fundamental to be changed.
The presenter admits the title is a bit clickbaity, but it’s all in good fun I think.
I think it’s interesting that the grayscale bit is basically completely unused, save for one game released only in Europe.
And I enjoy the whimsy of turning on grayscale mode and the “enhance green” bit and having it look not unlike a Game Boy.
But the obscurity of it, even in the system’s prime, is what interested me.