Like her, I used our Angry Birds stuffed animal as a guide.
I used the pumpkin Simplicity 2788 Toddler Costume pattern. The pattern went up to 4T and I was making it for a five and a half (that half is important to him) year old so I added four inches to the length and two inches on each piece around. I started with red fleece, tan fleece for the panel, yellow fleece for the beak and felt for the facial features. I eyeballed the shapes and cut them out.
I lined it with a silky polyester of some sort so it would slip on and off easily. I glued on the face shapes with Fabri-Tac. That stuff never comes loose. Then I stuffed and hand stitched on the nose and the tail. I didn't use the hat pattern. Instead I made a fleece beanie with the feathers on top. I stuffed it more full than the pumpkin pattern called for so he was nice and round.
I finished off the look with a green pig trick-or-treat bag. I eyeballed this one as well. I sewed a strap out of green felt then stitched the two faces together. The eyes, brows and nose are glued on with Fabri-Tac.
Now that he's done with the costume, we'll be putting it on eBay next fall. If you're interested in it, let me know! It would easily fit a child from 3 - 6 or 7.