The Paper Mario series is a series of Mario games published by Nintendo and developed by Intelligent Systems. They are 3D games, but the characters are drawn in 2D. They are based around platforming and RPG.
About the series
The Paper Mario series can vary from a platformer to an RPG. It is very similar to the Mario & Luigi series. It involves the player going through a game where everything has a "paper" sprite. Every Paper Mario game (except for Paper Mario: Sticker Star and Paper Mario: Color Splash) usually has eight chapters that the player must go through. There are currently five games in the series with Paper Mario: Color Splash being the latest installment.