I bought a couple of these Snuggies but always wondered about making one as it seems to be something that could easily be made.
When I was looking at the ones I bought, I was thinking about making a "pocket" in the bottom that you'd put your feet in. (Fold up a certain amount of fabric and sew at the sides.) I always seem to have a problem with any cover shifting and my feet getting cold air on them and not covered fully. Of course, I'd have to be careful about getting up and tripping!