Our 11 month old puppy started acting strange last week by barely eating, being extremely snugly to a degree she never has been, and carrying around her squeaky toys and whimpering. She would do it more and more often and eventually started collecting all of her toys on the couch and sitting with them. Last night she put all of them together and was bathing each one individually.
We went to bed and she didn't want to come, which was very strange since she normally does nothing but snuggle with us and our other dog. 
I got up this morning to go to work and found her like this.
After worrying about her a lot and researching the symptoms it turns out that dogs can have phantom pregnancies caused by a hormone imbalance and they start treating their toys like newborn puppies, carrying them around, creating a nest and snuggling them, bathing them, and crying when they're missing. It is both adorable and sad and makes playing fetch difficult because she acts like you just tossed her baby across the room and she freaks out about it.