I've watched the movie about 4 times, but I can tell you: that's NOT on the AGB! See the boot-up animation: "Game Boy" instead of "Game Boy Advance". Those graphics can't possible be on the GameBoy Advance, they're too good for that. It's fully 3D! And the resolution isn't AGB resolution.
Watch how Mario moves. Totally not-Mario.
My best guess is that this is a fake.