Pondering

How does someone who only ingests white milky liquid manage to excrete brown spinachy solids? What goes on inside those intestines that can turn the most benign liquid into the most foul solid? Anyone? Beuller? Beuller?

Since we're pondering lets also think on this: What makes said spinachy solid so aerodynamic AND precise allowing it to fly out of a diaper and land exactly precisely on diaperchangers toe and squirm it's way under the nail?