I've said it before and I'll say it again (and many more times, I'm sure): #1 is a different sort of kid. He's different enough that I've, without qualms, allowed him to sit up with me on the odd occasion and watch CSI and Criminal Minds with me -- something I will never be able to do with his brother.
He knows it's full of special effects, cool "dead body" makeup and he likes to discuss it all with me--often during the show (which is, admittedly, a tad annoying). What really captures his imagination isn't the "whodunnit" or the crime itself, but the science they use to solve the crime -- the concept of DNA and fingerprinting really flips his switch. A week or so ago, one of the episodes featured a lot of ballistics work. #1 turned to me at one point and said, "Is that true, Mom? Does every gun make different marks on a bullet?" He liked the idea that a gun could be "fingerprinted".
Which leads me to the "overheard" aspect of my post:
[#1 and #2 playing "guns" with imagination-fabricated Lego guns in their bedroom]
#1: "Oh no! The bad guy shot me!"
#2: "No, he didn't. I shooted you!"
#1: "No, you didn't. See? This is a bad guy bullet." (holds up imaginary bullet) "It has different marks on it than your bullet does."
#2: "No, that's *my* bullet."
#1: (patience clearly wearing thin) "No. This is the bad guy bullet. Every gun makes different scratches on a bullet and this one has the scratches from the bad guy gun." (emphatic huff)
[ Note: The overly defensive person in me has to say that my boys figured out the concept of playing "guns" all on their own -- actually, once #2 was old enough to interact well with his brother *he* seems to have started it all. Then again, he's the one who "taught" #1 the fun in imagining stuff in the first place! ]