I was stepping through the code of Pokemon Sapphire and I was especially
interested in what Game Freak's interrupt routine looked like. It turns
out that it looks almost exactly like the multiple interrupts routine with
user stack switching and cart interrupt handling that is in Jeff's crtls.
It looked like only the order (i.e. priority) of the interrupts was
changed.

So, I checked Super Mario Advance. Same code (except the priorities).
Now I'm starting to worry. People are so nervous about including
Nintendo's logo data, but disassembling code and distributing it is
apparently just fine.

Interesting things to note. I cannot find evidence that either game
copies its ISR to ram, yet they both attempt to handle the cart interrupt
by going into an infinite loop. This won't happen because the cart will
be gone. Pokemon makes an additional mistake of making the cart interrupt
the lowest priority, which would intermittently fail (Mario makes it top
priority). Maybe they do copy their ISR's to RAM, but the interrupt
vector is set to its load address in ROM instead of its VMA.

Anyway, I am wondering if this is all just an amazing coincidence, or did
someone copy nintendo's code?