Which studio developed the Nintendo 3DS port Donkey Kong Country Returns 3D?

Monster Games developed the Nintendo 3DS port Donkey Kong Country Returns 3D.

The original Donkey Kong Country Returns was developed by Retro Studios for Wii and released in 2010. Nintendo later commissioned Monster Games to adapt it for the Nintendo 3DS, producing Donkey Kong Country Returns 3D in 2013.

The port added stereoscopic 3D presentation and two play styles. Original Mode closely follows the Wii release, while New Mode adds assistance such as extra health and other helpful items. The 3DS edition also includes an additional world containing eight new levels.

Retro Studios therefore remains the developer of the original game, not the 3DS port. Rare developed the earlier SNES Donkey Kong Country trilogy, and Next Level Games is associated with other Nintendo projects, but neither studio made Returns 3D.