At first, I was skeptical...
...In the beginning when the Christmassy music was playing, but as it picked up and the zombies came in I thought it was great. Funny stuff, and awesome. I loved how you animated the running down the stairs, and the rooms passing in back of the main character as he ran, these 3D-like effects really added to it. I liked the letter part and the clown killing too. You get a five because:
Flash horror movies - rare
Fully animated characters in flash - rare
Funny and Horror together - rare
I hope you make the sequel man, it would be amazing.
Great stuff, keep it up!
Adam