I have a vast love for the Metroid series. It was the one I played with my parents when I was a toddler and such. I sadly only own Zero Mission and Fusion.
A friend of mine had told of me debug event text in Metroid Fusion, I have started a hack of Fusion to expand on it and I wanted this info for my ROM map. So he gives it to me, then I find what looks like a DrawText function near it and knew I was on to something. Faster forward 15 hours later, we had a full working Metroid Fusion debug menu. That NO ONE knew about outside of Nintendo for 11 years!
It's extremely powerful. I love Nintendo so hard.
So here is a video of it!
And so I also delved in the ZM rom for a bit.
While I didn't find anything new, I did look at Trunaur86s old menu hack for the on/off button.
When looking at the code, I discovered they intentionally removed access to it.
There's a register 'R6' which hold basically the onffswitch val. And the sets it to 0 and does checks to make sure it's 0, where as if it's non-zero you get the onoffswitch!