I really enjoyed playing this game. The movement felt great and I love the ability to either go around enemies or kill them. The difficult curve might be a touch high, but honestly it drove me to want to try again and again so I don't see that as being a major issue.
My only criticisms would be that the enemies and the dragon feel out of place and there isn't a lot of incentive for killing enemies. Personally, I am not a fan of having the mix of cartoon characters in a realistic environment, but that is just a preference. As for killing enemies, maybe adding a time bonus or something for killing them? I found it easier to just dodge the enemies rather than kill them. I like the idea of clearing obstacles with the fire ball, but with no real benefit to doing so I would only kill the enemies if it were convenient.
Other than those two things, this is a great game with a lot of replayability. The music and sound effects were spot on and with a few more worlds plus some added polish I could definitely see myself paying to play something like this.