Great first attempt
Instead of making still symbols and tweening them across the screen, try using a few more layers and make up the character models using those layers and making a walk animation (If that made ANY sense at all... hardly makes sense to me). I would probably recommend improving the intro. The sounds were a bit lacking and a bit too far apart. The intro doesn't have to be long but you got a good idea for yours. Just make it a bit shorter.
For a first submission, it's great. I know from experience it takes ages to make your first Flash so I can appreciate how the art is somewhat lacking.
What won me over was the Magic Roundabout theme when the bum kinda "introduced" himself.
Great work. Make more. I'll be interested to see how well you come along.