Fairly simple, but you post which characters are fighting then the next person says which would win, after which they come up with another match up. For example.
Ridley with no contest. Rather gang up with a blood-thirsty bad-ass dragon than a kid whom shoots energy out of his hand and transforms into different types...and shoots that type of energy.
Yoshi VS Baby Bowser (Woulda went Epona buuuuuut.....Epona just runs. :| )
Yoshi pretty much. He bested Baby Bowser in Super Mario World 2: Yoshi's Island, even with the help of Kamek on making him into a giant.
Ike vs Hector
I'm pretty sure everyone knows who Ike is already. If anyone doesn't know or played the Fire Emblem series, here's an image of Hector, one of the 3 main lords of the 7th installment, Fire Emblem Rekka no Ken (Fire Emblem).
EDIT- Forget it, might as well add a picture of Ike (in his grown up version) as well...