Making up an imaginary bedtime story with the boys, where they were going on an adventure to find a sunken ship with treasure, with the help of two dolphins. I started the part of the story where the boys put their
air tanks on and were going to swim down into the sunken ship with the dolphins. 

The 6 year old stops me... "Mom, this next part, where we swim down, find buried treasure and swim back up to the surface can take no more than 20 minutes" 
Me: 'Why?' 
Him: "Dolphins can only hold their breath for 20 minutes, so in the story that is as long as it can take before they need to come back to the surface"  

Even my imaginary bedtime stories have to stick to some scientific facts for plausibility for my 6 year old.

The 6 year old was shown a picture of a newspaper machine, and asked 'what is missing from this picture', his answer was the slot to put the money in to buy the paper.  However, he then proceeded to explain that no one really buys newspapers anymore and news is usually delivered through television or the computer.  This kid's comments crack me up, he is always listening and will throw together context clues from conversations months apart.  We should probably watch what we are saying, but it would be hard to always be on speaking patrol with this one about.