Number three: Dress up like a Wraith for Halloween
It was Halloween, Sheppard's favorite time of year. He loved dressing up like the scariest thing he could think of, and this year he had the perfect costume. He had bought white dreadlocks, and had made himself a Wraith mask. He was wearing the oldest, grossest, ugliest clothes he could find, along with some of Ronon's leather stuff he had "borrowed" the other day, and he thought the overall effect was pretty good.
He walked down the hall towards Weir's office, since she had paged him about something; she had said what it was, but Sheppard never paid attention. So, he was walking down the hall when he ran into Ronon. Ronon, seeing his worst nightmares come true, responded on instinct and years of experience, and shot him four or five times in a row, then began stabbing him until he was positive the Wraith was absolutely, irrevocably, thoroughly, dead. Weir, having waited for Sheppard to show up for twenty minutes and getting impatient, had decided to go to his room to see what was taking so long. Upon seeing Ronon over the body of a "Wraith," she became extremely annoyed. Sheppard had told her what he was doing, so she knew that it was him on the ground. She bent down and pulled the mask off, revealing Sheppard's face. She turned to the incredulous Ronon. "Ronon, it's Halloween, you dumbass." Apparently, no one had ever explained to Ronon what exactly Halloween was, because he began to stutter. "But- But- " Weir, thoroughly annoyed, did the only thing left to her; she smacked him upside the head. Hard.