Okay, not sure how much help I'll be, but from what I can tell, you want to access animation.as from Main.as.

What I'd do is import animation.as into Main.as, create a new instance of animation.as and then do what you want with it there. I don't know what's in Main.as so I can't quite figure out what the heck would be causing that wacky "undefined method animation" thing.

How have you been trying to get animation.as inside of Main.as currently?

Also, nice Bowser pinball sprite sheet, heh.