Stargate Atlantis/Recap/S02 E04 Duet

"I'm not crazy. I just have another consciousness in my brain."

- McKay

Searching a planet for survivors after a recent Wraith culling, McKay, Beckett, and the marine guarding them, a Lieutenant Cadman, are beset by a Wraith dart. McKay and Cadman are taken, but Sheppard and his group manage to shoot it down before it can make it through the gate. Unfortunately, they kill the pilot and damage the ship, leaving them no way of retrieving their captured people.

Zelenka is able to rig something up, but there is only power to rematerialize one of the two life signs detected. They go ahead anyway, and McKay appears and immediately passes out. They bring the rest of the dart back to Atlantis to begin the effort to retrieve Lt. Cadman. When McKay finally comes to, however, it turns out that, rather than being trapped in the dart, she is in fact trapped in McKay's head. Hilarity Ensues.

While McKay goes about arguing with himself, hitting on Dr. Beckett, and preparing for his date with sexy botanist Dr. Brown and Zelenka tries to fix the dematerialization mechanism enough to get Cadman her own body back, Sheppard is trying to make friends with Ronon Dex. Ronon is not terribly impressed by Sheppard's efforts, but decides to join the team after talking with Teyla. Sheppard in the meantime manages to wheedle permission out of Weir, and Ronon officially replaces Ford in main-character-ville.

Zelenka's efforts continue to produce little more than charred mice. On the upside, McKay's date meets with partial success, due mainly to Cadman taking over partway through (although it is hampered by her inability to keep his eyes off of Dr. Beckett). The strain of hosting two consciousnesses is starting to take it's toll on McKay's body, however. Dr. Beckett tells them that if one of the two doesn't "let go" it's only a matter of swiftly dwindling time until they have a fatal seizure.

In the midst of arguing over which of the two of them is going to make the sacrifice, McKay suddenly realizes that the dematerialization-rematierialization buffers from the stargate do basically the same thing as the Wraith transporter. He and Zelenka quickly macgyver the dart device and some of the gate crystals together, but there's no time left to test it on a fresh batch of mice. After a hearty kiss for good luck from a startled Dr. Beckett, McKay dematerializes into the Wraith device, and rematerializes as two not the least bit charred people. And there is much rejoicing.

Tropes

 * Grand Theft Me: it doesn't take long for Cadman to start taking over McKay's body against his will.
 * Hand Cannon: Ronon's is demonstrated for the first time here.
 * Jabba Table Manners: Ronon Dex. McKay might also be a mild example, and has to be coached by Cadman.
 * Mistaken for Gay: Beckett seems genuinely surprised that McKay's date is with a woman.
 * Now or Never Kiss: McKay Cadman and Beckett.
 * Playing Cyrano: Cadman really wants to play this role for McKay on his date with Dr. Brown, up to the point of exerting her Grand Theft Me powers when he fails to listen to her advice.
 * Professor Guinea Pig: Averted then played straight. Zelenka does all his testing on mice - who die horribly - but when McKay reconfigures the machine he can't afford the extra time to test it.
 * Rock-Paper-Scissors: McKay vs. himself Cadman. He loses.
 * Sharing a Body: McKay and Cadman.
 * Split Personality Takeover
 * Stock Episode Titles: 6 uses
 * Teleporter Accident
 * What Did I Do Last Night?: McKay wakes up naked and horrified in a strange woman's bed. Justified, in that Cadman took over once he fell asleep, and ended up just going home.