Is your ign a reference to light yagami, nah i'm probably overthinking things, oh yeah and the character limitation are removed as far as I'm concerned you might as well be the golden sonic, I'd prefer not to have anyone in our group represent mk.
On the ledge you quickly press down then jump and a direction. From there you can quickly attack with A or B. Sonic only has a few useful ones but It works with most characters and is a necessary skill. http://www.ehow.com/how_8507805_ledge-super-smash-bros-brawl.html