On October 6th you can pony up 200 Wii Points and download the Proto Man downloadable content. You'll then have full access to the yellow-scarfed character and all of his new game play moves.
Using Proto Man opens up a brand new mode that will allow you to experience the game in a slightly new way. Not only will you get to take control of Proto Man, but there are other small and unique changes that you'll notice as you play through the game again.
For starters you can't use Proto Man to achieve worldwide rankings or beat any of the game's challenges. What you can do is use Proto Man's unique game play moves, which proves to be a double-edged sword. The good news is Proto Man can now use his slide move to quickly slide under certain enemies and he can also charge up his shot for an added firepower burst. The bad news is that Proto Man takes double the damage of Mega Man and will get thrown back twice as far when he takes a hit thus making enemy encounters all the more tricky. You also will not be able to purchase special items like additional "E" and "M" tanks in the store. As you can imagine, this definitely ups the ante in the difficulty department.
According to Mark Bozon at IGN, using Proto Man does add a unique twist to an already amazing game and he seemed to really appreciate the unique game play twists Proto Man brought to the game, although he did emphasize that it does take some time to get used to controlling Proto Man as the overall feel is quite different from that of Mega Man.
If you're looking to add some replay value to Mega Man 9, this Proto Man content could be just what you need. And at only 200 Wii Points, it seems like a small price to pay to make an already outstanding game even better.
Check out a video of Proto Man in action: