ROM hacking

ROM hacks, or Hack ROM's, also known as fangames or bootlegs depending on the circumstances, are video games that have been edited or altered. Many fans distribute hacks of Mega Man games all over the internet.  Some of these games are hacked onto the actual game data. There is such a big number of hacks available on the Internet  (searching for Mega Man Hacks on YouTube will easily reveal at least a dozen).

Mega Man Ultra
Mega Man Ultra is a ROM hack for the game Mega Man 2 that was developed between 2005-2006 and released on 2006 as an edition to the game. The game features new enemies, music remixes from different games, more difficult levels and different named weapons, although the Robot Masters are still the same, only with a palette swap and different strategies.

Story
''20 years have passed, since the capture of Dr. Wily. During that time period, Dr. Light has been secretly creating a new battle robot called X. Six months ago, Wily escaped, and has stolen the blueprints to create X. Will Megaman find the truth behind Dr. Light and X...''

Notable Differences

 * All the Robot Masters are palette swapped. They also have much more different strategies than the second game, making their battles much more difficult:


 * Metal Man now throws much more Metal Blades (Saw Cutters) when he jumps, and when he goes to the other side of the screen.
 * Air Man shoots the Air Shooter (Top Spinner) faster and does a small hop before jumping twice to the other side of the screen.
 * Bubble Man now shoots more Bubble Leads (Ice Bubbles).
 * Quick Man shoots his Quick Boomerangs (Ultra Beams) faster and dashes twice the faster and twice the times.
 * Crash Man won't stop shooting Crash Bombs (Vector Claws) if he is attacked.
 * Flash Man now runs twice the fast and when he uses the Time Stopper, he shoots more shots than he does in the original game.
 * Heat Man now charges more energy before shooting himself at Mega Man, and shoots himself twice the fast. After that, he may get stuck in a wall, trying to shoot flame blobs but unable to do so, making him very vulnerable to attacks.
 * Wood Man shoots his Leaf Shield faster, it makes more damage, and he jumps to the other side of the screen directly, giving almost no time to be attacked but only in the air.
 * The Wily's Great Temple bosses have also different strategies, and others are also replaced by other bosses, except for Mecha Dragon, Guts-Dozer and the Wily Machine No. 2:
 * Mecha Dragon is now weak to the Bubble Lead (Ice Bubble) and it is the only weapon capable of harming it.
 * The Picopico-kun is replaced by Metroids, and they are also interestingly enough to the same weapon the original boss is weak to: the Bubble Lead (Ice Bubble). This is a reference that in the original game, Metroids are very weak to the Ice Beam.
 * Guts-Dozer is now weak to the Leaf Shield and now shoots Crash Bombs and Ultra Beams. However, it deals minor contact damage.
 * There are now 10 Boobeam Traps, and they now shoot at intervals. They are also now weaker to the Quick Boomerang (Ultra Beam).
 * The Alien holograph is replaced by a Mega Man, that then transforms into some kind of a jet powered Mega Man that shoots supercharged electrical spheres that spin and now deals slightly more damage.
 * Many enemies are ripped from other Mega Man games and programmed to do what the normal enemies do, the only exception being Wood Man, who has the Super Mario Bros. baddies as the enemies on his stage. The other enemies are also back but others are also palette swapped.
 * The position of the bonuses and the levels is very different.
 * It is implied that Mega Man kills Dr. Wily in the game, as when the game is cleared, a robot (maybe X) is piloting the Alien holograph.