Molly does it too! Especially as her way of greeting me when coming back home from errands/outings, visits from my daughter, grandkids, etc. She bounces, runs around barking in greeting and at times falls out the door. More like rolls out. It's hilarious to see.
She does this when playing too. She really looks and sounds funny when she's grabbed one of my socks while running around with it. And, also when she sits/stands and shakes her head rapidly so that the sock is flying back and forth and flopping against the side of her head accompanied by her growls. Now that has me laughing.
