I used an old mask I had as a kid for the general idea. I held a piece of paper up to my son's head to get the spots for the eyes and nose right.
I backed the mask in black felt for two reasons, One, for thickness, and two, because I wanted to make the nose part black to look more realistic. Unlike the original that was a separate piece, I kept this all together.
I cut a slit in the back to make sure it could poke out so the kids could still breathe through their noses and it would lay better on their faces. I just sewed some black elastic between the layers and stitched the two pieces together all around the edge (except the teeth that were not backed) and around the eyes.
As for my Hamburglar costume, three parts were homemade.
The hat is one I made several years ago for my Puss-in-Boots costume (which apparently I never posted). I thought about remaking it to make it more sturdy and to stick out flatter on the bottom (more like how the Hamburglar's is), but decided to skip it. It would be fine. I just added a removable ring of yellow fleece around it instead.
The tie was not perfectly constructed. I sort of copied the shape of one of my husband's ties in a long piece.
Then I sewed it to a ring to go around the neck and made a fake knot in it. The elastic was so that I could pull it over my head.
Each of the hamburgers were just pieces of fleece that I sewed a small brown piece of felt on. I used some wonder under to attached them all to the tie.
For the mask I copied the basic shape of a sleeping mask (courtesy of JetBlue from a recent flight). I tweaked in a little to make it look right and the sewed the elastic in between the two layers.
Definitely not saving the best for last, the chicken in Harland Sander's bucket. In order to make my husband's costume seem complete, we decided a bucket from KFC was needed. One we had it we decided it needed more. So, I last minute sewed together some chicken pieces. They are not too pretty, but they did the job well.