I do not own Atlantis or anything having to do with it, please don't sue me, blah blah blah.
This story takes place during season 1. I haven't seen any of season 2, and I have only seen the first 6 or 7 episodes of season 1, so PLEASE don't tell me what happens later on!
The planet was empty. No life, little vegetation, not even any ruins. Major Sheppard was getting a little bored waiting for McKay and his small team to finish studying what they were doing, which to him seemed like absolutely nothing. But Major Sheppard knew better than to ask McKay when he was going to be done. He knew McKay would start yelling at him and rant about how important his work was. He was talking with another person, on the team for the same reason as Sheppard, which was in case there were the Wraith or any other hostile lifeform. Most of their conversation focused on the upcomming negotiations on another planet.
McKay and his team finished their work and approached Sheppard. "There seems to be no sign of any life existing here that would have usedthe Stargate."
Sheppard felt relieved. "Oh cool, now we can go?" McKay nodded and told his team to come to the gate.McKay dialed, and they approached the gate. As the first few scientists entered, McKay's bag swung out of his hand and landed in the dirt. "Seriously Major, must you always do this kind of thing?"
"What are you talking about?" Sheppard asked. "I didn't touch your bag."
McKay picked it up. "Uh huh. That's what you always say." He stepped through the gate, followed by Sheppard. After a few seconds, they found themselves in Atlantis, their home.
"Well Elizabeth," McKay began, "We didn't find anything on this planet. It doesn't look like there ever was any life." McKay walked to his lab, tossed his bag down, and quickly recorded what he saw on the planet, which was nothing of interest. When he finished, he left to go to a weekly meeting with Weir, Sheppard, Ford, and Teyla.
When the lab was completely empty, McKay's bag unzipped itself, and a rock that McKay did not place inside it transformed into a silvery liquid, about eight gallons. It then took human shape and transformed into a perfect replica of McKay. The imposter exited the lab and walked around Atlantis.