Paper Bowser Jr.

Paper Bowser Jr. is the incarnation of Bowser Jr. that appears alongside Bowser Jr. in the game Mario & Luigi: Paper Jam he represents Bowser Jr. from the Paper Mario: Sticker Star. Alongside various other paper characters, Paper Bowser Jr. came out of a book containing a whole paper world. Bowser Jr. was previously depicted in a paper form in the four Paper Mario: Sticker Star, but there is nothing suggesting that those games took place within the book world introduced in Mario & Luigi: Paper Jam

History
Paper Bowser Jr. makes his debut as a wholly unique character from Bowser Jr. in Mario & Luigi: Paper Jam. He first appears at Bowser's Castle, meeting the real Bowser Jr. but unlike the two Bowsers Bowser Jr. and Paper Bowser Jr. quickly resolve their argument and become friends. Later they on guard patrol watching Peach and Paper Peach, making sure they don't escape, they also steal the book in attempt to destroy it, they get sent to the Villa in Mount Brrr and after a Papercraft battle, they fight the trio in Bowser's Castle then lose and are heavily injured on the floor Bowser and Paper Bowse come to yell at the two Bowser Jr's but when they see that they can barely move or speak this makes them so angry and picks them both up and they aren't seen again for the rest of the game. Though it could be possible that Paper Bowser Jr. was forced to return to the paper world.