What's All star mode?

All Star Mode is where you choose a character and battle against every one of the 25 characters. For the first few battles, you're against one person, then two, then three!

You'll see three hearts, DO NOT USE THEM! (they're the only ones you'll get!) After battles you might even see a trophy sometimes, and if you pause where you can see it, it looks really cool! When you go against Mr. Game & Watch, because he's alway's last, you'll go against 15-30 of them. (not sure which) You'll get a really cool trophy when you win.

HOPE I HELPED!
Mr Mario 4 U

Once you unlock all the playable characters you will also unlock all-star mode, it is kind of like classic but if you die you lose, you have 3 hearts to heal yourself in between each battle, run out of hearts and your in trouble.

All-Star mode is the third One-Player mode along with Classic and Adventure. It is where you battle all 25 characters in the game. When you start it you will see three Heart Containers. DO NOT USE THEM! You will need them if your characters % goes up. You character cannot heal him/herslef after battle. It isn't really that tough on easier difficulties but it's tough on harder difficulties of course.

All Star Mode is how you can test yourself using only three Hearts vs. Every character of the game (Mr. G&W, Roy, Mario, all of 'em.) Use your best character (most choose Roy or Link) to try it out the first time, and use your Hearts wisely.