Paper Bowser

Paper Bowser is the incarnation of Bowser that appears alongside Bowser himself in Mario & Luigi: Paper Jam and it is the main antagonist of the game. Alongside various other paper characters, Paper Bowser came out of a book containing a whole paper world. Bowser was previously depicted in a paper form in the four Paper Mario series games, but there is nothing suggesting that those games took place within the book world introduced in Mario & Luigi: Paper Jam.

History
Paper Bowser makes his debut as a wholly unique character from Bowser in Mario & Luigi: Paper Jam. He first appears at Bowser's Castle, confronting the real Bowser and getting into a fight with him. Eventually, however, they decide to join forces and kidnap Peach and Paper Peach, subsequently returning to the castle and summoning Petey Piranha to slow Mario, Luigi, and Paper Mario down.

Eventually, the two Bowsers plot to betray the other and imprison them in the book, though not before they trap the Mario Bros. in the book and destroy it. The two merge together into Shiny RoboBowser, only to be defeated. Paper Bowser makes one last attempt to grab the book, but Paper Mario reaches it first, and the Mario Bros. trap him back inside.