Great atmosphere! The concept is really cool and you pull it off quite well, i never thought i'd be scared by a cat leaning his head into a doll house. The song(?) that loops in the background gets a little annoying. The sudden cut off is quite jarring and stops the music from ever blending entirely into the background. Your art is decent and the camera angles and lighting were pretty good too. I think your animation needs work and a lot of it is far too static. Remember than when people walk and run they don't glide, they move up and down. A key part of making run/walk cycles look good is getting this right. Having a body glide horizontally along with legs moving beneath just looks bad, make sure the body is moving up and down with the rise and fall of the walk!
That said some of the animation was pretty good and i'm sure with practice you can get some create some more realistic looking motion. The voice acting fitted the concept perfectly and the sound design was good too.
I didn't really like the shrinking growing scene, the imagery of it is a little too cliche and comical to work with the sinister tone you're creating here. All in all though it was an enjoyable flash and i look forward to future episodes!