Official Nintendo Magazine, has strongly hinted upon a third playable character within it's awesome 10 page review of Super Mario Galaxy 2: 

•  Galaxy 2 takes place in an alternative reality, where the events of the first game haven't taken place - Mario and the Luma's have never met. 
•  Mario helps out a big Luma who owns the new Spaceship Mario - he needs power stars to fuel the ship. 
•  Peach has gone walkies...with Bowser. 
•  There'll be 40+ galaxies to explore. 
•  Springo Mario only makes 2 appearances. 
•  Luigi becomes playable once you earn around 20 stars. 
•  Another character is strongly hinted at once you've topped the 120 star mark. 
•  A monkey called "The Chimp" introduces mini-games. 
•  Many references to classic Mario with a good amount of ingenious 2D sections.      

So we don't know the third character then? What about that Green Hill Galaxy rumor? WTF does "gone walkies" mean? They went out and bought some walkie talkies? 

" So we don't know the third character then? What about that Green Hill Galaxy rumor? WTF does "gone walkies" mean? They went out and bought some walkie talkies?  "

Tingle.

Toad?
 
It's Nintendo, they'll not introduce an all new character. It'll be someone we've played as before in about a dozen games in the past. Kind of loses the "OMG SECRET THIRD CHARACTER!" appeal once you realise that :(

" Tingle. "

Play with your Mii.

" Toad?  It's Nintendo, they'll not introduce an all new character. It'll be someone we've played as before in about a dozen games in the past. Kind of loses the "OMG SECRET THIRD CHARACTER!" appeal once you realise that :( "

"WTF does "gone walkies" mean? They went out and bought some walkie talkies?  "

A third character!?!
 
OH SNAP. IT'S REAL!
 

Ivy from Soul Calibur 4.

My bet is on Wario. 

" Unbiased and professional print publication"
 
was this sarcasm? because if not, why the hell would you feel the need to say that, why not just say "Official Nintendo Magazine"

Unfortunately it probably won't be anything cool. I remember the 'secret' opponent in Punch Out, and how they wanted it to be kept super secret, and it turned out to be Donkey Kong (I think). So my bet is that it won't be anything exciting, and it'll probably be something stupid like Toad or Donkey Kong, although I'd be satisfied with Wario.

Maybe it's Princess Peach, that way she can finally save herself.
 
She hasn't been playable in a while, so that would be cool.

I read about that last night.  I'm curious about who it is.  It better not be Sonic though...

The third playable character is... love.

" The third playable character is... love. "

My bet's on Princess Peach. Unless Nintendo pull something really crazy and drag in a character from another franchise (which I don't think they'll do) then she seems to be the logical choice. Bowser and Wario seem too bulky and heavy to compete with the jumping skills of the Mario Bros. and Toad seems to be a little lacking in that department as well, besides who would want to collect 120 stars to play as Toad? Peach has the unique ability to use her umbrella to hover across gaps and when talking about main characters in the Mario series that aren't the Mario Bros. this does seem to make her the best fit. Of course all this is assuming there is a third playable character.

You should make this as a poll.  My bet's on Toad though.

It's not going to be anything out of the Mario universe.  So it's probably going to be someone like Toad or Wario.

Most likely it's going to be Wario. I have a feeling that they're going to pull a super mario 64 x4 here.

"

My bet's on Princess Peach. Unless Nintendo pull something really crazy and drag in a character from another franchise (which I don't think they'll do) then she seems to be the logical choice. Bowser and Wario seem too bulky and heavy to compete with the jumping skills of the Mario Bros. and Toad seems to be a little lacking in that department as well, besides who would want to collect 120 stars to play as Toad? Peach has the unique ability to use her umbrella to hover across gaps and when talking about main characters in the Mario series that aren't the Mario Bros. this does seem to make her the best fit. Of course all this is assuming there is a third playable character.

"

Their making a new Mario Brother, Gino.

" @Gamer_152 said:

"

My bet's on Princess Peach. Unless Nintendo pull something really crazy and drag in a character from another franchise (which I don't think they'll do) then she seems to be the logical choice. Bowser and Wario seem too bulky and heavy to compete with the jumping skills of the Mario Bros. and Toad seems to be a little lacking in that department as well, besides who would want to collect 120 stars to play as Toad? Peach has the unique ability to use her umbrella to hover across gaps and when talking about main characters in the Mario series that aren't the Mario Bros. this does seem to make her the best fit. Of course all this is assuming there is a third playable character.

"

I thought she used her dress to float? She didnt have an umbrella in SMB2."

" @Meowayne said:

" The third playable character is... love. "

I've heard from some people that's all you need. "

Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels.

" Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels. "

" Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels. "

Geno....

" @ryanwho said:

" Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels. "

Wario's big mechanics are the dash, the butt stomp, and being able to pick up and throw stunned enemies. The but stomp is now part of marios aresenal and i dont think the dash would be game breaking or anything. "

Ummm, so does anybody actually know who the third character is?

" @Supermarius said:

" @ryanwho said:

" Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels. "

Wario's big mechanics are the dash, the butt stomp, and being able to pick up and throw stunned enemies. The but stomp is now part of marios aresenal and i dont think the dash would be game breaking or anything. "

He's never been a jumper, though. Which is why he couldn't just sub in for any given Mario level, unlike Luigi who was originally a pallete swap. It would be weird seeing him jump. Wario continuity is super important uguys. "

Man, I forgot the awesomeness that was the JET HAT. 
 
Warioland was great. 
 
But yeah, him or Peach, I guess...  Maybe some other character that they introduce in Mario Galaxy?

" @ryanwho said:

" @Supermarius said:

" @ryanwho said:

" Wario's mechanics are so fundamentally different, I dunno if that's really possible unless they're giving him Wario specific levels. "

Wario's big mechanics are the dash, the butt stomp, and being able to pick up and throw stunned enemies. The but stomp is now part of marios aresenal and i dont think the dash would be game breaking or anything. "

He's never been a jumper, though. Which is why he couldn't just sub in for any given Mario level, unlike Luigi who was originally a pallete swap. It would be weird seeing him jump. Wario continuity is super important uguys. "

He was a jumper in all the warioland games and wario: shake it. 
 
Here he is jumping in his first game, Warioland (excellent game, btw)
 

"

I just got 120 stars. I did not get a 3rd character. It's possible that it has yet to come though, as it appears there are... 
 

" I just got 120 stars. I did not get a 3rd character. It's possible that it has yet to come though, as it appears there are... 
 

SPOILER WARNING: Click here to reveal hidden content.

Another 120 stars that are green and appear when you hit 120.
 

"

So, who was it?

Having Peach playable once you save her as non-canon bonus would have been nice.