Goomba only needs two plate appearances on offense to clear his three non-Wall-Ball missions (as far as I know, you can't get Hit and Sac Bunt on the same play).

Bowser Jr. encounters, which are fast and respawn every time you play a match of baseball or any minigame, can provide a character with 1 plate appearance on offense per encounter.

Goomba is 4th on the DK Kongs initial lineup.

If you add all of this information together, you get this rather wacky route: an RNG-manipped Jr, a game of Wall Ball, and then a coinflip Jr that needs to be in your favor or your run instantly dies.

This run is a fair example of what the endgame of this category could look like in the future; obviously, many little things could be faster, and I got the worse of the two possible Jr scenarios at the end, but this is basically how it should go.

I play on Special difficulty rather than Star because Bowser Jr encounters on Special use batters later in your default batting order, meaning we get to Goomba sooner.