Worlds Collide

Worlds Collide, originally known by the much longer title Sonic & Mega Man: When Worlds Collide, is a 12-part crossover storyline between the franchises Mega Man and Sonic the Hedgehog announced on the San Diego Comic-Con International on July 10, 2012, published by Archie Comics' Mega Man, Sonic the Hedgehog and Sonic Universe comic books in 2013.

The event apparently takes place in the future in Mega Man's timeline as the main comic was only up to the events of Super Adventure Rockman at the time, while Worlds Collide features Bass, Beat, and Tango, and references Duo and Nitro Man. In addition, Mega Man also expressed confusion about the Genesis Unit's presence, as he had completely destroyed them from what was implied to be a long time beforehand. The explanation for this is that Wily used the Genesis Wave, a power with the ability to alter reality, to cause a time-skip.

Mega Man

 * Mega Man and all those from his world retain no recollection of the event as said world was restored to nearly as it was before. Mega Man himself, briefly recalled Worlds Collide only to forget it upon the Genesis Wave's effect being undone. After effects include:
 * Dr. Wily despite forgetting everything had an urge to stop on a carton of eggs, due to left over feelings of betrayal from Dr. Eggman. Incidentally, his video logs had no recollection of Dr. Eggman or the Blue Chaos Emerald.
 * Proto Man regressed back into Break Man. His damages to Mega City, Mega Man, Bomb Man, Guts Man & Cut Man was undone.
 * Ra Moon was back and functioning.

Sonic The Hedgehog

 * Sonic the Hedgehog, Dr. Eggman and Blaze the Cat remember the events, with Tails remembering it not long after things were restored. Due to Eggman's interference, however, Sonic's world changed greatly in contrast with Mega Man's world. Several characters ended up in different locations. (Sonic the Hedgehog #252 & Sonic Universe #55) Examples include:
 * Sonic and Tails went from being in the Northern Tundra (where they were Pre-Genesis Wave) and were brought back to New Mobotropolis.
 * Amy Rose (who doesn't recall Worlds Collide) went from being in the Northern Tundra to the Sol Zone with Blaze.
 * Dr. Eggman, along with Orbot and Cubot went from being in the Northern Tundra to the Efrika Plains. The remains of the Egg-Wily Machine X ended up there as well.
 * History in Sonic's world has also been altered. One example of such is the events of the video game Sonic Colors being canon, as well as that being the last time that Sonic & company saw Silver the Hedgehog.