There were these things called bathrobes. They even had a belt thing that went around them so you could secure the bathrobe to yourself and walk around.
You know.. a Snuggie looks a LOT like a bathrobe that's just been put on backwards – now THAT is some brilliant thinkerizing and inventering.
How much do you want to bet that the Snuggie was "invented" during a drunken coordination-less attempt to put on a bathrobe?
I know, you're thinking "but a bathrobe won't cover my feet like a Snuggie!". and you're right. Fortunately, life isn't a medieval-combat video game where you're only allowed to wear on piece of clothing that covers your legs – you can double up and put a normal blanket over your feet (or even slippers), giving you the freedom that only a Snuggie commercial seems to be able to offer.