Nice work! I instantly died on mickey, but up to there was pretty neat. Waluigi and Dry Bone's toilets were pretty tedious, but Bowser's felt like a proper boss fight. If you want people to complete your game, I'd recommenced adding a save feature.
I think bite sized, unique projects like this don't get enough credit. Nobody's going to make it if they spend all their time making their dream game, shipping completed products is the most valuable skill a game dev can have.