Dark Bowser

Dark Bowser is a clone of Bowser, created by the Dark Star. Its first appearance was in Mario and Luigi: Bowser's Inside Story as the final boss, fought by Bowser. He then appeared later to seek revenge, after his defeat and was reborn thanks to the The Dark Star X. He was then defeated by the Mario Bros. Later he reappeared in OiramOiram12345 and The Dark Star X and Mario defeated him. Near the end of the movie, he and Bowser X defeated Bowser and the merged with OiramOiram12345 and the DSX to form Dark Bowser X. Mario defeated Dark Bowser X and it also fought Bowser while Mario fought Dark Fawful X in his belly. Dark Fawful X lost and Dark Bowser X split up into the people who merged to become it. Dark Bowser transformed back into the Dark Star, then merged back with the DSX during the final battle between MarioMario54321 and OiramOiram12345.