Bow-Wow

Bow-Wow is an optional sidekick character that can be found at the end of Moblin Keep. The translator apparently felt that he was some kind of dog, even though he looks nothing like one.

Bow-Wow will prance around the screen and eat enemies like there's no tomorrow. He can also eat the flowers blocking access to Bottle Grotto, but since these can also be burned by the Magic Rod he is not necessary to complete the game.

Taking Bow-Wow to his owner's house will remove him from the party permanently and initiates a cutscene in which Marty gets smooched. This does absolutely nothing for you game-wise, but whatever floats your boat, I guess.

Keeping Bow-Wow with you reduces the difficulty considerably, although it's not like the game could get much easier than it already is.