[This is a review of "SMB: Hanshin Tigers - Giabbit Hunting", a ROM hack of the original Super Mario Bros.]

This is one of the countless versions of SMB1 that's on this multicart.
Named after the Japan Baseball team, although I'm not sure if they're actually tied to this officially or not, this game is just a single custom level.
Coins are now stars and all enemies are Giabbits, the mascot of their rival team, the Yomiuri Giants.
The game has two endings, the "bad ending", in which you defeat the final boss (which I'm not actually sure what it's meant to be) without fireballs (which are now baseballs, obviously), freezes your game.
The good ending, which you get by throwing fireballs at the boss, doesn't freeze your game.

It's weird.
That one level is pretty difficult all things considered, but since it's pretty boring to sit through I say it's not, like, entirely fun. The game runs weirdly slowly on GBA so it's quite floaty.
If you find it on a multicart like I did (in which it was titled "Wario adventure"), I'd recommend playing it, but it's not worth seeking out.