This happened awhile ago, but I didn't think to put it here until now.
One day my roomie and I had gone somewhere together and when we got home we got out of the car and the neighbors dog was barking. Funny thing was though, it barked a familiar tune- "Woof-Woof-Woof, Woof-Woof-Woof, Woof-Woof-Woof Woof-Woof!" With a bewildered look on my face I said to my roomie "Did that dog just bark a Christmas carol?" To which my roomie responded "Yes, Jingle Bells!" Yep, the dog had barked Jingle Bells. We both heard it. My roomie thought it in her head, but doubted the possibility, but the fact that I heard it too and expressed it aloud proved it was not a figment of our imaginations.