So I read on a couple reviews that it seemed like an oversight for Nintendo to create a single-player with only Donkey Kong himself, or a fake co-op mode with a second controller. I just discovered that if you start a co-op game and then restart that same campaign/save game in single player-player, you'll have your Kong Partner with you anyway and they'll just ride your back without the need for you to control two controllers. (I have a Pro Controller and Gamepad in addition to a Wii Remote, so it was less of a struggle for me but still a pain in the butt).
Tested it for myself. Just thought I'd share for anyone who wants to have the benefit of the Kong on your back without the two-controller straddling baloney.