Famicom/NES Version differences
Karnov was released for the Famicom on December 18, 1987 in Japan, and a year later on its North American equivalent, the NES, in 1988. Although it plays very similarly to the original arcade game there are some noticeable differences:
Karnov takes two hits to die instead of just one. After being hit once he will turn a blue color in which he has one hit left or can gain an extra hit back by grabbing a blue fireball orb.
The Super Fireball is replaced with the Spike Bomb which destroys every enemy on screen. The Trolley item is replaced with the Shield which is used to reflect an enemies fireballs.
Levels 4 and 8 are completely different from the arcade levels.
The final boss is different. Both fights, however, take place in similar rooms.
There are also non-game play differences between the Famicom and NES versions. The Famicom provides a story throughout the entire game, complete with images. The NES game does not have such a feature. The Famicom game is also considerably more difficult since it does not allow the player to continue after all lives are lost. The NES game, however, provides unlimited continues. The NES game also allowed Karnov to be killed when both the A and B buttons were pressed on the second controller.
Source: Wikipedia, "Karnov", available under the CC-BY-SA License.