Dark Ditto
Background
Evil version of Ditto McCloaker, think he's from Anti-Space or one of those Bizarro worlds.
Good Timeline
Gamehiker Member OG
He emerges in the Gamehiker Member OG series as the main villain of Gamehiker Member OG IV. First he poses as Count Dittof and takes custody of Masamune, Vorpal and Slort following the "death" of Ditto McCloaker (implied to have been caused by Dark Ditto, but it was later revealed that Dark Ditto had actually marooned Ditto in England). Dark Ditto then ventured to become a god by turning all of the OGers into RPers so he could rule over them like a god. When that failed, he tried the more obvious route by stealing and eating the Cheesecake of the Gods. However, Dark Ditto was ultimately defeated by a hooded figure claiming to be Ditto McCloaker.
Dark Ditto returned in Gamehiker Member OG VII: The Undiscovered Subtitle, where he led an underground group of heroes and villains against the recently-formed cult of disgruntled sidekicks. Biou Guiseppie and the other sidekicks attempt to execute Dark Ditto at one point, but he is later saved by the heroes.
Galaxy Goers
In the year 2015, Dark Ditto was whisked away by a mysterious figure from the future known as the Darth. The Darth first brought Dark Ditto to 2065 and showed him a first-person perspective of Earth's destruction. Then Darth brought Dark Ditto to 2345 and had him serve about Masamune's Bladechappe in Galaxy Goers. Dark Ditto receives various improvements in the following battles; first he is upgraded mechanically into Ditto-Tron, and then he is given Force powers to become known as Master Ditto.
Master Ditto later betrayed Masamune, leaving him for dead in the vacuum of space, and marooning his crew on the planet Syntax. Through the magic of time travel, Dark Ditto had become the Darth. The Darth then took the Bladechappe back in time and became the person who initially gave the Bladechappe to Masamune. The Darth made various trips across the timestream and, aside from bringing his past self to the current time, he also adopted Luigi of the Stars as his son.
Bad Timeline
Not much is known, other than he appeared as a villain near the end of Member OG 10. While aboard Lupus' sinking robot, he fused with Cat, becoming Black Cat. Nothing is known past that; he is presumably dead.