Space Fever

Space Fever is Nintendo's own (unauthorised, hence no copyright notices on-screen) clone of Taito's Space Invaders. In order not to come off as a blatant pirate copy, it introduces a range of Nintendo-specific touches:

Taito's aquatic-themed aliens are replaced by chickens, cats and dogs (or pigs?)

The "heartbeat" backdrop sound is replaced by a more intricate beat.

The bonus UFO scores lower and flashes in seven colours.

There are 12 instead of 11 columns of aliens.

Three modes of play are available:

A: The aliens move not in one, but in two blocks which split up and join together again.

B: The game start with just one row of aliens, but as they move downwards, new rows are added from behind.

C: Basically the same gameplay as Taito's original.