Carlin (also, Karlan) was the personality stamped onto Dr. Daniel Jackson on the planet P3R-118. (4.10 "Beneath the Surface")
Carlin was assigned to do maintenance of the tools and equipment in the plant. His personality was very similar to Daniel's when it came to the need to know the truth and not stopping until a puzzle is solved.
He spent nearly every minute of his time with Kegan. She often showed him physical attention, touching him affectionately. Whether or not they were lovers remains a mystery, but they appeared to be at the very least close friends. She took him under her wings to train him after his transfer from the mines.
Because she was so attached to Carlin, Kegan was very jealous if he showed attention to someone else. She especially got upset when he started to hang out with Jonah and Thera. She threatened to withdraw her friendship from him, but he continued to pursue trying to find out if Jonah and Thera had been his friends in the past and why he couldn't remember.
Carlin was bold in his dealings with others. He engaged Jonah in a fight when Jonah grabbed Kegan's arm after she had refused to serve Thera bread. Even after this encounter, however, Carlin did not hold the incident against Jonah and continued his pursuit of questioning their former relationship.
When the pressure built up in one of the boilers and threatened to destroy their section of the plant, Carlin stepped in to take charge. He instructed Kegan to evacuate the area and procured large metalic mallets to break the pipe to relieve the pressure. He knew that the pipe would be too hot to handle. He and Jonah pounded on the valve until it broke, causing a large, forceful release of steam which Carlin ducked to avoid. Jonah helped Carlin up and it was at that moment that a hint of Daniel's trust for Jack emerged.
Carlin's dreams included seeing Jonah and the Stargate at the SGC, as well as Kegan warning him not to go with Jonah to "the other side". Because his dreams included Kegan, he must have valued her friendship very much. Even still, he continued to spend time with Jonah and Thera. Kegan expressed her disapproval, but Carlin didn't stop this socialization. This was another inner trait of Daniel's as he has shown obsession with his work at the expense of his personal relationships.
Once Brenna told them their true identities, SG-1's memories quickly returned, although Daniel did call Jack "Jonah" after being told his name. While Jack revealed the existence of the domed city to the underground workers, Kegan expressed doubt, but Daniel/Carlin insisted that she believe them. After Jack showed the city to them by shooting out one of the skylights, Kegan reveled in the sunlight. Carlin/Daniel helped Brenna to the Stargate to get to the infirmary after she suffered a gunshot wound in her effort to help SG-1 escape. (4.10 "Beneath the Surface")
--DeeKayP 20:07, 13 Jun 2005 (PDT)