U.S. Patent and Trademark Office. The company said the request was made "in honor of the upcoming Nov. 21 launch" of Donkey Kong Country Returns -- in other words, Nintendo is about to put a lock on the phrase's commercial use: "On Nov. 21, It's on like Donkey Kong™!"
Of course, Nintendo still seems to encourage non-commercial uses of the exclamation, clumsily describing it as "an old, popular Nintendo phrase that has a number of possible interpretations depending on how it's used." For example, listen how the phrase completely changes when you add a "beeyotch" to the end of it.
[Image credit: Vinteeage.com)