Disclaimer: I don't own Stargate Atlantis or the X-men franchise. That's a good thing.
Note: Spoilers for "Critical Mass". Assumes an established Sheppard/McKay relationship.
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"Would you quit fiddling with your neck! Dr. Beckett did a thorough scan, and there is absolutely no chance that you've got a Goa'uld in your head."
"You sure?"
"Any self-respecting Goa'uld would take one look at your hair and find another human to infest. Doesn't one of us own a comb you could use?"
"I'm not dignifying that with a response."
"You just… Never mind. And speaking of missing things, just how do you know so much about hydroelectric engineering?"
"Huh?"
"The word 'spillway' just flitted off your tongue today like it was a word you used everyday. Since when do you know so much about dams and spillways?"
"I don't know. Maybe I read about them somewhere."
"Or maybe you're the one who stole my copy of X2…"
"Well, you're the jackass who got to see the third one in theaters, and what were you doing hiding the DVD under your bed?"
"Because I know you, and I know the ending of the second film would drive you crazy until you saw X3, and it isn't out on video yet, nor is it still in theaters, so even if you did go back to Earth and got permission to leave SGC, you still wouldn't be able to see it, which would drive you crazy, which in turn would drive me crazy."
"So you're saying you deprived me of Famke to protect me from myself."
"Exactly."
"Jackass."