See... they can behave when they are in close proximity to each other. Actually, it's probably because it's the first time they've been out of the house in a while (escape's to the garage don't really count).
Here's Millie in her 'about to escape' spot. It doesn't matter if the garage door is open or not. She did this all winter. It's funny because they never go outside through the garage. That is a privilege reserved for ME.