A few pointers
The bad: It's really short, not very smooth and could have had better graphics
The good: Mario won, suitable music. You seem to have a basic animation skill level. Keep trying, you can do well!
Reviews for "Mario Vs. Bowser Jr."
Eagh
It's...... its ok? Try harder? I don't know, you didn't intend for it to be long obviously. lol
Question
how do you cut your sprites?