Mario
You don't need a certain amount of stars, levels, etc. Go to the 2nd Snow level and go up to the snowman's head and get blown off. Your hat will fall off. Instead of getting your hat, go over to the tree closest to the water. Touch the tree (don't jump on it) and stand. You should be warped to another tree.
If you don't warp, touch a different part of the tree. When you do get warped, go get your hat. Mario will say, "Here we go!" twice and grab his hat off his head. He'll keep it in his hand until you either leave the level or warp from one of those tree to another.
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