First of all, get the feather that lets you turn into winged koopa. then proceed to the 3rd level of the mountains, and survive with the wings. Once you get to the boss door, go in. Jump towards his car while holding space bar. If you can get the corner of his car, you will jump up again, and no matter what you do, don't let go of the space bar. While doing this, always aim for his head, and dont mind the icicles, those wont bother you. With this, you can defeat him in about 30 seconds.