They have to have happened during gameplay. They can be funny, weird, badass, or whatever. Try and avoid anything story related, as that would be spoiling it for those of us who haven't finished the game yet.
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In GZ, I rescued Paz first since I find it to be faster than getting Chico then Paz,I placed Paz on the starting cliff area. I went to Chico taking out guys & rescued all the PoWs & Chico at the top right coast LZ. I was wondering why the mission didn't end after I extracted Chico. I forgot all about Paz on a cliff being drenched in heavy rain and started laughing.