Be prepared and have a thinner flannel shirt on hand just in case Mother Nature decides to gift a warm Halloween evening.
Astronaut
Astronaut suits are always puffy and you can fit a sweatshirt and sweatpants underneath without looking odd.
Animals
There's nothing odd about seeing a bear, deer or squirrel with a little extra plush this time of year.
Construction worker
You could really just consider any profession that works outdoors in the winter, but a construction worker is a good place to start.
Princess
If your kid is determined to wear a Disney princess dress, Frozen is probably the way to go.
Ghost
Go more traditional with a ghost costume. Their sheet-like structures have plenty of room underneath for multiple clothing layers. Matching white or black gloves and boots are easy to add.