I'm sorry...
I want to put this as nice as possible:
The song has been done to death, and you didn't really add anything to it.
The use of a character singing was nice, but you used all images you didn't even make and just tweened them.
That is not animation.The character was animation, and if the cartoon was more centered around him it would have been better. It was hard to watch him and concentrate on the cartoon. But I like that for your animation, you actually did some character work and lip syncing. Even though it has been done to death, I would have given you a better score if you actually animated something besides the character,and brought something new to it.
It would be pretty easy to beat legendary frog's and his is the best version out there.
In the constructive criticism side of things, you got a good score because people like the song, not because your cartoon was any beauty to watch. If you want to practice, that is great, I love seeing people practice, and creating whole cartoons is a great way. BUT, I do not reccomend submitting cartoons just of tweened images.
I say try doing some frame by frame cartoons, or if tweening is your way, make some nice character models and try animating a dialogue between two people.
I hope I could help :)