Sorry, but at least you tried.
I'm sorry, I know you meant well, but this flash is really not very good. I'm not saying it because its a sprite movie, I'm sayng it because it is an excessively sub par sprite movie. I actually like sprite movie, but there are a good few things in yours that really could use improvement. Lots, and lots of improvement.
First of all, I'm a sprite editor. I like to make edits of sprites to make them look like other characters or things. I know you didn't make the edits you used, and I know where those sprites came from. On the original sheets, they looked great. However, you don't seem to know how to cut/copy and paste very well. The sprites were horribly resized, and it looks like you were using one of those tracing select tools, which would explain the excessive amounts of the spritesheets' backgrounds ripped with the sprites themselves.
Learning how to use transparence or make a selected color "opaque" (in this case, the 'background' color) would help, rather than trying to trace around the sprite with a different selector tool.
Also, when resizing sprites, never, ever, EVER use any other increments than 50% and 200% to halve and double the size, respectively. If one resizing with one of those isn't enough, do it again with the same number. Don't stretch and shrink sprites on your own, it looks terrible in the end. Use an automatic resizer. MSPaint has a decent one.
Next, music was really not that great. A lot of the time it went to from quiet to loud, and back to quiet from song to song. A lot of the music didn't even feel right with the SSBM stages you used them in.
If you can fix the music quality, as well as your sprites, it would be a big improvement.
Animation itself, you at least know you you're not that great at animated violence (or apparently just animating in general).
If I came off as offensive and insulting in my review, I didn't mean to sound that way. I'm just trying to help you, and in order for you go get the right help, you gotta get the blunt truth.
So I hope my review helps you, if even a little.