T1, E1: Emperor penguins cross a treacherous frozen sea to reach their breeding grounds. They must lay their eggs without touching the ice. Rockhoppers brave the world's stormiest seas, only to come ashore and face a daunting 300-foot cliff. Humboldts are strange tropical penguins that have rarely been filmed. The hard work for all the penguins finally pays off when their tiny, vulnerable chicks begin to hatch.