Aang
The plot they described relates with the first and second episodes of the series, where the "water people" (Katara and Sokka) find the "air guy" (Aang) while "trapped in a snowy wasteland" (the Southern Water Tribe) with "some fire people [that] are pressing down on them" (Fire Navy and Zuko). The creators of the show made Aang to be frozen in an iceberg for 1000 years. He was to wake inside a futuristic world, where he would have a robot named Momo and a flying bison named Appa. The creators lost interest in the theme, and changed it to 100 years of suspended animation. The robotic Momo was changed to a flying lemur, and the herd of bison was reduced to one.