Bubble Bobble Part 2 (NES)

Bubble Bobble Part 2 is, obviously, a sequel to Bubble Bobble, though its "Part 2" status is debatable.

Unused Title Screen
Graphics and 16x16 metatiles for an alternate title screen can be found in both the Japanese and US ROMs. Though the actual screen layout no longer exists, the ending scene (which was based on the old title screen) can be easily modified to show what it probably looked like. It's worth noting that the logo fits perfectly inside the existing cloud arrangement.

The image on the left shows the palette used in the ending scene, while the one on the right shows an unused palette, which is identical aside from the purple color seen in the logo.

Early Graphics
Older versions of some existing graphics can be found in unused areas of the Japanese PRG ROM.

HURRY UP!
Ditched in favor of a complete character set. The lower half of the 8 and the 9 are much blockier than the final versions.

Skel-Monsta
Judging from this lone tile, it appears that Skel-Monstas used to be much more evil-looking.

Bubble
Bubbles used to be solid, similar to their arcade counterparts. The solidity might have made sprite flickering more apparent.

Corn Dog
Two colors were swapped on this cholesterol-laden treat.

Enemy
Another sprite that had its colors swapped.

Roc
Roc got a glossy coat of paint and bigger shoes for his official debut.

Super Drunk
Nothing but a palette swap for this pushover of a boss.