Rockman vs Donkey Kong

In the movie as the title, Rockman confront with Donkey Kong. Although the contents themselves begin with the opening of Rockman, why is Donkey Kong present at the stage that you choose on the first screen for some reason, you confront Bonce with Donkey Kong.

The result of winning and losing is as follows.
YouTube - Megaman vs Donkey Kong

By the way, as a similar meaning unknown collaboration by the producer of this movie, I do not know what Tetris is saying that Mario 's stage is clear, but there are movies meaning as well as words.

YouTube - Tetris-Mario