I Wanna Be the Guy: The Movie: The Game, commonly called I Wanna Be the Guy and abbreviated to IWBTG, is a freeware platform game created by Michael "Kayin" O'Reilly for Microsoft Windows using Multimedia Fusion 2.

[1][5] IWBTG has unusually difficult platforming elements, unorthodox level design, and uses sound effects, characters, and music from many other games.

IWBTG is made up of several stages split into many screens, which are mostly pastiches of Nintendo Entertainment System games, such as Tetris, Ghosts 'n Goblins, The Legend of Zelda, Castlevania, Kirby, Mega Man, and Metroid.

The first seven bosses (Mike Tyson; Mecha Birdo; Dracula; Kraidgief, a parody of palette-hacked character glitches; Mother Brain; Bowser, Wart, and Dr. Wily in the Koopa Clown Car; and a mix between the Mecha Dragon from Mega Man 2 and the Yellow Devil from Mega Man and Mega Man 3) are adapted from classic games, mostly platformers, but their behavior and appearance have been modified and enhanced for IWBTG.

Alongside a traditional range of recognizable dangers, such as spikes and pits, there are many less obvious threats as well, most of which are all but impossible to avoid without either previous knowledge or trial and error (such as Tetris pieces and "Delicious Fruit", which can fall downwards, upwards, or sideways).

Thus, to complete the game, the first six bosses along each path must be defeated before the warp screen will allow the player to access the final area.

The entirety of the plot is given in a message during the opening credits, a parody of bad Japanese translations and broken English in early NES games.

[18] Two months after the release of IWBTG, Kayin announced a prequel titled I Wanna Save the Kids.

[1] The remaster was acknowledged by Kayin himself, citing it as a "best case scenario" and a "perfect package for anyone who wants to play IWBTG who isn't some super specific game 'research' type".