Welcome to "How to Talk to Your 3 year old about Cannibalism" 101:
1) You don't.
2) If you must, keep it short and light.
3) Be sincere and vague.
4) Know that you will probably contradict yourself and confuse your child.
Now that we've covered the basics, let's explore the following case study:
Mom makes paninis for dinner one recent evening using George Foreman grill (little known use for such device, but works great). Dishes cleared and mom moves grill near sink to cool off and clean later. As mom is drying her hands, a child calls for her and she turns to respond. She doesn't realize how close her arm is to hot grill and so she burns herself. Youngest child hears muffled cry from mom and runs to see if she is alright. Mom assures child she is okay, child empathetic and curious and begins to ask questions: What happened? Are you okay? Does it hurt? Can I see it? Can I touch it? Why not? Did you cook it? Can I eat it? Why not? Mom responds to each question with simplicity and candor, but the 'why not' after her final answer leaves her stumped. She recalls a previous conversation where she played around with her son about eating him and he got a bit frightened. Is that why he's asking? She then remembers that she recently watched a movie about a cannibalistic serial killer. Did her son somehow sneak downstairs and hear of this gruesomeness?
Questions for you: Should the mom explain any further? Into how much depth should the mom go? Is the mom thinking too much?
No need to answer. Before the mom could form any kind of response, the son looks at her, grins and says, "I'm just joking."