Spin Ground-Pound
I don't know if this is a cheat or not, and it doesn't do anything special, but I just wanted to tell if no one else knew. Ok, to do this, jump into the air (any height doesn't matter), and spin. Right after (immediately, instantly, super fast right after), press Z. Mario will look like he's in crouching position, for 1 second, then go downward for a ground-pound. It looks cool, but I don't think it does anything.
More tricks, tips and cheats for this game are right here - Super Mario Galaxy cheats
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