While not technically part of the robot...
We were testing one day when our battery ran out. We pulled it out of the robot and asked one of the new kids to go back to our the room and get us a new one. He only saw one other battery, and it was half-charged.
I believe his thought process was "I can transfer the power from one half-charged battery into another half-charged battery to make a fully-charged battery! Hey, these connectors look like they can be plugged into each other..."
(Someone noticed just before he tried this and yelled. We all still have our limbs attached
)