Some of the bosses (and some of the regular characters for that matter) can be a real pain in Mickey Mousecapade, but with a little prep they're pushovers.

In the very first stage, you're going to want to take the time to get the second Star, which goes to Minnie.

Then, carefully using ladders you can actually get the two mice separated

And, since Minnie's invulnerable, you can use her to attack enemies while Mickey hangs out at a safe distance

And if you didn't bother getting that star at the beginning, well then you're out of luck.