Here's an actual Couples Snuggie in action.

And here's the Couples Snuggie at rest. It is as large as a couch and resembles a fleece elephant with that third armhole in the middle.

Academy Award Hosts Alec Baldwin and Steve Martin relax backstage in a Couples Snuggie while awaiting their next appearance on stage. They were likely screening Hurt Locker.

Actually, the Couples Snuggie, aka Snuggie for Two, aka Double Snuggie, has three arm holes and less material between the two people. This appears to be a hybrid they put together, and closely resembles a mini-snuggernaut.
I have recently received my first Double Snuggie submission, which I'll post soon so you can see the three arms, design, etc of the actual Couples Snuggie.

Snuggie for Two

Update: 2/11/2010 - It appears HSN has sold out of the Double Snuggie. It looks like you can get them at the Amazon Snuggie Store.

I monitor all things Snuggie via Google alerts and suddenly everyone is writing about a Couples Snuggie. Not to be confused with the Siamese Slanket. I am trying to get info on where this Double Snuggie is available.