Mario and Luigi: Dream Team has been in development for three years, and it’s because the characters are drawn using 2D sprites rather than 3D models, the game’s developer, AlphaDream, revealed in an Iwata Asks interview.

Development was unusual in that AlphaDream created alpha, beta and even gamma versions prior to locking down on the final product. This was primarily due to the fact that AlphaDream were aiming to achieve a stereoscopic 3D effect using sprites rather than 3D models, and this was easier said than done.

“We worked out special ways of drawing and using color to make them look three-dimensional. The work load was tremendous, but thanks to that, it has the sort of smooth polish distinctive of AlphaDream,” says Akira Otani, a producer at Nintendo.

In particular, larger characters would make the flatness of the sprites stand out. In particular, the game’s bosses contributed to this issue. Furthermore, the amount of work increased substantially when AlphaDream decided not to simply mirror the sprites in the game, and to create unique mirrored sprites for both Mario and Luigi.

“On the Nintendo DS, there were about eight directions, but for the Nintendo 3DS, we made pixel art for 16 directions,” says Hiroyuki Kubota, who was in charge of the game’s script and direction. “What’s more, Luigi’s hat has an L on it, so we couldn’t simply mirror the data.”

Sano adds, “Likewise with Mario, he always raises his left arm when jumping. Simply mirroring him was off the table because the gesture would be backwards.”

All-in-all, it took about five or six people to create Mario and Luigi’s animations alone.