» Tue May 17, 2011 9:20 am
"Cool story, bro" is best used when someone explains a huge idea they have, but which obviously pointless and no-one cares. (Or for pointing out trolls.)
It's like saying "Ohhh, that's nice" really sarcastic.
It likely originated on a certain site that cannot be mentioned.
I'm sure that the new search tool called Google could tell you more.
edit: and i was even ninjad!