What is the best DVD or book that teaches toddlers about stranger danger?

I have an overly-friendly 3 year old that will hold hands with any stranger and talk their ear off. She often tells random people how much she loves and misses them. I love her outgoingness, but realize that I need to really instill the importance of Stranger Danger in her. Any suggestions on good DVDs or books that I can use as teaching tools? She seems to really grasp things that she learns via the TV well.