"The most fun to do in the weightlessness is going down the ladder headfirst, walking on the ceiling, chasing after M&M's that you throw up into the air - they're just bouncing around all over the place and you go around like a fish eating them. I often tell kids that when you go into space and experience weightlessness, the serious adult in you gives way to the child you used to be, who had imagination, who had no bounds on what was possible."