The Game Boy version of "Baseball" was one of the first games available for Nintendo's handheld. It includes Mario and Luigi as captains. Mario himself is featured on the cover.
Mario and Luigi are captains of the team; Mario is the captain of the Bears; Luigi is the captain of the Eagles. You can select them as your pitcher if you want, but graphically all the pitchers look the same. The rest of the team pitchers have common English names, such as "Paul","Randy","Sam", and "Jimmy."
During this era, Nintendo would often include Mario in games just for appearances to help sell the game, you often don't really control Mario in many of these games. Other examples of this is Mario is the ref in Tennis, the paddle in Alleyway.
Nintendo re-released the NES version of baseball for their short lived GBA e-reader attachment. The game came in a pack much like a pack of baseball cards. There were a total of 5 cards that had to be scanned by the e-reader in the correct order. On the back of each card provided screenshots of the game as well as tips and instructions.