Did you know Donkey Kong in DK Country Returns is a 2D character?

[JWeinCom]

For those wondering, a 2.5 D platformer is a game where characters can move into the fore or background BUT they are limited to movement on a 2D plane.

A good example of this style of gameplay is Kirby 64. In that game, you stay on a strict left/right path, but that path does move into the foreground and background to give you an illusion of depth. DKCR on the other hand is a strictly 2-D platformer.