Cosmic Reset Button

The Cosmic Reset Button is a mechanism that was incorporated into the Death Egg Mark 2. As its name suggests, its purpose is to reset reality in order to suit the plans of Dr. Eggman, which it does by launching the Genesis Wave. Either the same or a different/newer version was later incorporated into the Wily Egg, which also launched a Genesis Wave. It seems that only the power of a Chaos Emerald can activate it, as each one ran on a Chaos Emerald, and after the first one's emerald disappeared, the button would not work.

Genesis - Operation: Clean Sweep
Dr. Eggman first used the Cosmic Reset Button to alter reality on Mobius, creating a far simpler version of the planet. However, Super Sonic was able to undo the effects of this initial Genesis Wave, and the button was rendered inoperable for a time due to the loss of the Chaos Emerald that provided its power source. Additionally, when the effects were undone, the original world was reset by ten seconds. This time reset initially confused Dr. Eggman as he pressed the button seemingly for the first time; however he began to recall the events and realized what had happened. The button was located aboard Dr. Eggman's Death Egg Mark 2 and was pressed while it hovered above New Mobotropolis.

Genesis II - Worlds Collide
Either the same one or a new one entirely was later used by Dr. Eggman and his new partner, Dr. Wily - who had located the missing Chaos Emerald in his own dimension - to alter both of their realities as part of their alliance against both Sonic the Hedgehog and Mega Man. It was located aboard the two doctors' Wily Egg and was pressed while the flying fortress remained in their own pocket zone, the Skull Egg Zone. This time, the resulting Genesis Wave did not effect the zone it was present in, but instead two other zones entirely - Earth 20XX and Mobius.

Trivia

 * It is unknown if the Cosmic Reset Button and resulting Genesis Wave effected the entire Prime Zone or just the world in which it was on/near, Mobius, which exists with the Prime Zone, but it is interesting to note that the first Genesis Wave returned Julie-Su to the Twilight Cage, which seems to be a pocket zone on Mobius.