|Out of universe information|
- "The more someone told him not to do something, the more he had to do it."
- —Elizabeth Weir
Janus was one of the most well-known and brilliant Lantean scientists, and his inventions were never orthodox advancements. He took great pride in creating out-of-the-ordinary technological marvels, most of which were either banned or frowned upon by the Lantean Council. He installed a time machine in one of the many Puddle Jumpers in Atlantis, and hid many of his controversial inventions and research (such as a component of the Attero device) in his secret laboratory. He also designed a personal cloaking device and made use of Long-range communication devices and Long-range communication stones. (ATL: "Before I Sleep", "First Contact", "Identity")
When Major John Sheppard and Dr. Radek Zelenka were killed when a Wraith Dart destroyed the Time Jumper and crashed into Lantea's ocean, Janus was able to save Dr. Elizabeth Weir and became her advocate when she met with the Lantean Council. While he argued and defended Weir on her behalf that she should be allowed to return to her own timeline and prevent the Atlantis expedition from falling into the same tragedy again, High Counselor Moros and Melia refused, and Moros angrily condemned his experiments, ordering the Timeship destroyed and the city to be evacuated. (ATL: "Before I Sleep")
Refusing to allow the future Atlantis Expedition to walk into the same disaster she herself had faced, Weir pleaded to Janus to help her find a solution that would save the expedition from walking into the same disaster she faced with herself. Janus agreed and, after doing some calculations, concluded that manually rotating the Zero Point Modules sequentially every 3.3 thousand years would allow slightly more power to be available when the city was visited by the Atlantis expedition and Weir decided to stay behind in the city to perform the task. Janus programed a stasis pod to re-awaken Weir every 3,000 years or so to allow her to manually turn the ZPM's. He also programmed a Failsafe mechanism into the city should power drop to such a critical level that the shield would fail, so that the clamps keeping the city at the bottom of the sea would release, and the city would rise to the surface, He also blocked all gate addresses except for earth so that no one except someone from earth could find Atlantis. (ATL: "Before I Sleep")
As Weir decided to stay behind, Janus himself decided to escape with the rest of the Lanteans to Earth with the hope that his efforts to save Atlantis for the future Atlantis Expedition would succeed, and was the last Lantean to leave Atlantis. Sometime after arriving on Earth he rebuilt his timeship, which would later be used to destroy a Goa'uld mothership and eventually retrieve a Zero Point Module from Ra, which was later used to shield and save Atlantis from the Wraith attack. (SG1: "It's Good to Be King", "Moebius, Part 1", ATL: "Before I Sleep", "The Siege, Part 3")
Shortly after finding Project Arcturus, the Atlantis expedition discover Janus's protege, Ikaros, a teenage genius who worked with Janus in developing Charybdis, a reality-warping supercomputer that they believed could be used to change history so that the Iratus bug would never evolve, thus preventing the Wraith from existing. However, Janus abandoned the plan because he believed that Ikaros was becoming too obsessed after his family was killed in a culling. (ATL: "Mirror Mirror")