Remember the Blendy Pens commercials? You put two different markers into the "Fusion Chamber" and then you could produce a multi-colored drawing. Our kids were always mocking on the way the announcer talked with an exaggerated voice.
http://www.youtube.com/watch?v=JqY9zD3P0HA
After our son went through 5th grade reproductive health, we asked him what he had learned and if he had questions. He said, "Well, basically we learned that the mom and dad go into the Fusion Chamber and produce a baby!" Thank you, Blendy Pens!