My mom's friends are staying for a bit, they have a 5 year old girl. 

She told me that she likes light up toys, so I decided to get an RGB LED, a AAA battery, and a boost converter. 

She held the two wires to the battery while I held the wires to the positive and negative parts of the LED, and I showed her how each positive lead resulted in a different color. 

Her mother then got into it, so I had her hold the battery while I held the negative part of the LED in place and I asked the 5 year old to make purple out of the two appropriate colors.  The parents were extremely happy and almost grateful that I taught their daughter something. 

Even though I technically had their daughter touch exposed live wires, 5v live wires, but still.