There have been a number of ROM hacks of Balloon Fight, varying from changing graphics, characters, stages, or other things. However, none of them are made with Nintendo's approval, and in some instances can be found on pirated Famicom multicarts and even built in to some "Famiclones" or "NES-on-a-chip" systems.
Air Umbrella/Zero Gravity Edit
This hack is relatively simple, only replacing graphics, characters, and the title screen. In this hack, the Balloon Fighter now appears to be a young boy with a transparent umbrella, and Balloon Birds are now humans, or possibly aliens, who fly using propellers on their heads. Balloons are replaced with bubbles. Clouds are now UFOs, and Platforms and the ground now look more metallic and artificial. The logo on the title screen now says "Air Umbrella" and is pink, and the copyright date for Nintendo is now completely missing. Other minor changes include the score counter and phase number being blue, and the water looks slightly different.
There's even a sub-sub-hack, where it's "Zero Gravity", but 2-player and Balloon Trip mode are blanked out, which is present on the Retroplay Plug N Play 200.
Balloon Mario Edit
This hack only changes the Balloon Fighter to look like Mario. The sprite resembles the one used in Super Mario Bros., but with the smaller body of the Balloon Fighter. The background is now blue, and because of the palettes overlapping, yellow Balloon Birds now have gray faces and red overalls. There appears to be two versions of the hack, one with a green title and one with the standard orange.
Board Fight Edit
This is a slightly more advanced hack, where all of the level designs are new, and there are now a total of 16 phases. The phases now loop back to phase 1 instead of 4, and later levels feature palettes and graphics which are completely new, with some levels taking graphics from The Legend of Zelda II: Adventure of Link. Players also begin with 20 lives, and do not get Balloons back at the Bonus Stage. The title screen now has the words "A bunch of folks present Board Fight", as well as the two Balloon Fighters standing below the title. The title screen retains the 1984 copyright from Nintendo, but adds a new line with copyright 2015 "A Bunch of Folks".
Cosmic Balloon Assault Edit
This is another hack similar to Board Fight, even made by the same person. There are only 12 phases, but all of them are new, with some graphics from Hello Kitty World and Super Mario Bros. 3, and the phase loop goes back to phase 1. The players start with 6 lives.
This is the first published hack of Balloon Fight to change the level layout, and was released alongside documentation on how to hack the game and change level layouts.
A somewhat advanced hack which replaces the music and graphics. All characters are some kind of fish, all background elements are sea-themed, such as being coral, seaweed, etc., and Clouds are squids. The music plays through the whole game, even through pauses and the title screen. The music only stops temporarily at a game over, and sometimes during the title screen demo. The title screen is completely unique, with a custom "Fishwar" logo. Balloon Trip mode is absent, and the Nintendo copyright is gone, replaced "BBG".
There is an alternate version which has different music and Balloon Trip mode, although it isn't marked, replaced by the words "Push Start".
Another version exists without two-player mode or Balloon Trip, which is on the Retroplay Plug N Play 200.
Joust More Edit
Many characters and graphics have been replaced with Joust-themed sprites. The water has also become lava. The title screen uses the original Balloon Fight font, but now with the title "Joust More". The Nintendo copyright has been replaced with "Hack 1998 Grimlick", and Balloon Trip is now "Joust Flight".
The hack was made because of the similarity between the gameplay of Balloon Fight and Joust, and the title might be interpreted as meaning that you should play Joust more often, or that Balloon Fight is essentially an extension of Joust.
Satoru Iwata Edition Edit
After Satoru Iwata had passed away, a fan hacked Balloon Fight in memory of him, making him the main character. The title screen is purple, Balloons now have faces like Kirby, and the game modes have become "1-SatoruIwata", "2-SatoruIwata", and "IwataSan Trip".
The hack was featured in a magazine called Nintendo Force, and there are even reproduction cartridges of the game.
There appears to be multiple versions of the hack, with a later version featuring art of Iwata with Balloons on the title screen.
Super Mario Balloon Edit
The Balloon Fighters have been replaced with Mario and Luigi, and Balloon Birds are now Koopa Troopas, using sprites similar to Super Mario Bros. 3. Stage palettes have been redone to fit Mario level themes, and the background noise of the Balloon Birds tweeting has been altered. The title screen now has a more Mario 3 style font, and adds a 2014 copyright for Magnus Nilsson, along with a line dedicating the game to someone named Mymis, while still keeping the Nintendo copyright.