It turns out that Digital Museum has some secrets that we didn't know about. First off, it's possible to activate a 2-player mode on the Grandia All-Star Pro Eating Contest minigame by going to the title screen for that game and pressing Up, L, R, and A simultaneously on the second controller (which takes you to the character select screen and highlights player 2's currently selected character with a blue arrow).

There is also a code you can enter on the title screen for Gadwin's baseball minigame - first press Left, then Right, then press X 12 times. If you did it right, you'll hear Gadwin's "hmph!" sound. If you start the game, you'll see that Rapp doesn't pitch the ball. What you can do now is toggle the throw type (indicated by the counter above Rapp) with Left and Right, and press B to trigger a throw. The C button is used to swing the bat. No lives are taken away if you miss a throw, essentially making this a hidden "practice mode" for the minigame.