Bubble Bobble

Bubble Bobble is an arcade game by Taito, first released in 1986. It was ported soon for numerous home computers and game consoles. The game features two Bubble Dragons, Bub (Japanese "Bubblun"), who is green with yellow spikes/horns and Bob (Japanese "Bobblun"), who is blue with cyan spikes/horns. Together, they journey through the Cave of Monsters to rescue their girlfriends. They move over a system of platforms, busting and pushing bubbles, avoiding enemies and collecting a variety of power-ups.

Moon Water storyline
On the original Game Boy version of Bubble Bobble, and Classic Bubble Bobble for the Game Boy Color, there is a storyline in which only Bub is involved in the gameplay.

In this uncommon storyline, Bob (as a human) has an unknown sickness, so Bub has to pass through the hundred levels to defeat Super Drunk and get the Moon Water. There is no mention of the "Cave of Monsters" in this version.

In Classic Bubble Bobble, Bob (as a bubble dragon) has the unknown sickness. Bub has to go through a number of levels (lesser than the arcade or Game Boy, etc. versions) and defeat the Darkness Drunk in order to gain the Moon Water. Again, there is no mention of a "Cave of Monsters".