Yeah, Robio is right.

Check out this trailer, they show what Yoshi can do

He runs a bit faster and can get various fruit power-ups. One increases his speed, another makes him a baloon.

http://www.wired.com/gamelife/2009/06/shigeru-miyamoto-interview/

Wired.com: Unfortunately, I’m planning on writing everything. And I have another sharp question: Super Mario Galaxy 2. I was surprised to see this announced, because as was said, typically Nintendo doesn’t do two Mario games on one console, and beyond that it’s a very straightforward follow-up with similar levels, which is something that we rarely see in the Mario series. Why the change in philosophy that says it’s ok to do a sequel?

Miyamoto: The biggest reason is because we simply hadn’t run out of ideas within the system that we’d created for Super Mario Galaxy. One of the biggest ideas that we felt we didn’t take good enough advantage of in the first one was “China Syndrome,” or the idea that if you drill a hole straight through the earth in one place, you would end up on the other side, so if you drill a hole from Tokyo you would end up in New York. We had some elements of that but the first thing that we did in Super Mario Galaxy 2 was to create the drill item that you saw in the trailer. We felt that as soon as we completed the drill item and began playing around with it, we felt that with just that one item there was a lot that we could do that would really make the game a lot of fun.

Wired.com: You’ve added Yoshi, which is something that people are really interested in. How does that change the gameplay mechanics?

Miyamoto: In Super Mario Galaxy, one of the features of the game was the pointer functionality — you were able to point at things in the game, and grab onto them, and pull yourself through, and things like that. We felt that was somewhat similar to one of the things that Yoshi could do, and in bringing Yoshi in, it felt like a new approach to it and that there was a lot of fun that could be had.

I think it’s kind of difficult for us to have Mario running around and carrying things in the world, but by incorporating Yoshi there’s a variety of different ways that we can have Yoshi carrying things and using that as a new gameplay element as well.

Wired.com: Super Mario Galaxy was also the first time where we saw a story in a Mario game that was more than just window dressing, that was a really interesting narrative. Are we going to see more of that?

Miyamoto: I’ve talked to (Galaxy director Yoshiaki) Koizumi about that a lot, but this time I’d like to go with as little story as possible. I’ve always felt that the Mario games themselves aren’t particularly suited to having a very heavy story, whereas the Zelda series is something that lends itself more naturally to that idea. We’ve differentiated a little bit between those two, because the Zelda games have had an in-depth story whereas the Mario games have not. Mr. Koizumi is the type of person who, whenever we’re working on a new Mario game, he always wants to bring more story elements into it, as he did with Super Mario Galaxy. But in talking with him this time, he agrees and feels that with Galaxy 2, there won’t be a need for as deep of a story.

I think you did see a person carved out of a tree stump in the trailer. That person has a bit of a story.

Wired.com: When I talked to Mr. Koizumi, he said that he would try to sneak in story elements without you knowing.

Miyamoto: Well, I put a stop to that at the beginning, this time (laughs).

Wired.com: Why do you think that Mario games aren’t served by having a story?

Miyamoto: I just feel that the Mario games are something that should be a much more bright and active experience. The games are much more of a physical action type of game. My feeling is that with the Mario games, you don’t need to have such a complicated setting where you have these particular characters with complicated backstories that can weigh down the bright and fun feel of the game. So in that sense, I feel that even if all that you have is that the villain is just simply a villain and you fight them, and you throw them down, and you find out, well, that wasn’t such a bad villain after all, that’s enough story for ultimately what is just about a very fun experience.

I think what’s really the most ideal thing is for the player themselves, within their own imagination, to carve out what they view as being the essence of the character. With New Super Mario Bros. Wii as well, we’ve had some battles over the story elements. They always want to have these dramatic scenes where Princess Peach gets kidnapped, but I always tell them, no, it’s fine — Princess Peach likes cake, so you can just have them use cake as bait to kidnap Princess Peach, and that’s enough. I was thinking they could have these big ships come in, and they’ve got these big chains all over them, and they drop a plate down with cake on it (laughs).