! You're on Game Boy Camera
Game Boy Printer: Model No. MGB-007
Designed to go with the Game Boy Camera, this was a large (compared to the Game Boy Pocket) thermal printer. If I remember correctly, it originally retailed for $60. It required 6 AA batteries and used proprietary rolls of paper, which could be purchased anywhere the Printer was available and ran about $10 a piece; rolls of paper are still available at Nintendo's web site. It interfaced with the Game Boy via a garden variety Link Cable.
Like the Game Boy Camera, this was low quality black and white fare, but these obviously weren't designed for Ansel Adams, and for their purpose they worked nicely. Also note that the Game Boy Printer found its way into connectivity with a few games, such as The Legend of Zelda: Link's Awakening DX, which allowed you to print pictures from one of the features added in the game's colorization. Presently it's discontinued, although rumors of a first party successor to the Game Boy Camera continue to make their rounds, so there may be hope for the Game Boy Printer Advance yet.
Cool Game Boy Printer trick: Hold the FEED button as you turn the Printer on for a nice, paper wasting "Hello." Nothing that'll threaten the Turing Test, but your printer loves you.