This calm old man was a resident of Makapu Village and, like all the other residents, had complete faith in Aunt Wu's predictions. He stayed calm while being attacked by a platypus bear because Aunt Wu told him that he would have a safe journey.
When Aang, Katara, and Sokka first met the calm man, he was being attacked by a platypus bear. The group saved him, and inquired why he had not simply run away; he answered that Aunt Wu had predicted he would have a safe journey, and that she had never been wrong. He proceeded to hand Aang a package, stating that Aunt Wu had instructed him to give that to the first person he encountered, and continued on his journey. The package turned out to be an umbrella, which came in handy when it started to drizzle shortly afterward. The group ventured to Makapu Village, where they saved the town from being destroyed by lava of the erupting Mount Makapu. When Sokka challenged the beliefs of the villagers in Aunt Wu's predictions once more, it was the calm man who pointed out to Sokka that Aunt Wu's prediction that the village would not be destroyed had come true, as the volcano had not destroyed the village, causing Sokka to say "I hate you." Katara quickly pulled him away, saying, "It's okay, Sokka, everything's going to be alright."