M2J was a planet in the Pegasus galaxy that had either a Stargate or a Spacegate. In 2008, Lt. Donovan and his team, as well as Dr. Radek Zelenka, visited M2J where they were the guests of honor at a diplomatic dinner.
While they were on the planet, back on Atlantis, the Sakari AI took the form of Zelenka to ensure Dr. Rodney McKay would find the seed carrier on the ocean floor. The AI's explanation for Zelenka's early return was that three members of Donovan's team suffered a severe allergic reaction to whatever was in the food on M2J, and that he suspected little green berries with purple specs on them, which made his tongue numb. (SGA: "Remnants")