If Final Smashes were really based on a characters most trademark move then Fox would have the airwing, plus Link's would of probably been Fierce Diety Link.
It makes perfect sense, Brawl simply chooses a random, but great, move a charcter uses and puts it into the game as their final Smash. Besides, the the developers may of thought that the the Mega Mushroom would be too similar to the Super Mushroom item, and the Airwings to similar to certain assist trophies.
Black
Name: Chris
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