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Lake is an evolved chimpanzee who appears in War for the Planet of the Apes' '.
Birth and Childhood
Lake was born in Muir Woods Park to unknown parents, around the time Blue Eyes was born. Lake and Blue Eyes were close when they were children and played all the time, until Blue Eyes started wanting to be with boys his age and hunt.
War for the Planet of the Apes: Revelations
When Blue Eyes was leaving with Rocket, Ray, Malcolm, Ellie and Alexander to search for threats South, Lake approached him asking him if he was going to leave without saying goodbye. Blue Eyes said yes and Lake was angry at him because of it and how clueless he was being. Blue Eyes was mocked by his traveling companions because of his cluelessness to Lake's attraction to him.
War for the Planet of the Apes
Lake is presumably Blue Eyes' soon to be wife as she greets him when he arrives after a long journey and they lovingly touch heads. She is also shown sitting alongside the Ape Council with her head on Blue Eyes' shoulder. She speaks up that it is impossible to move the entire colony overnight.
Later at the labor camp, while several of the other apes shun Caesar, Lake gently tells him to "forgive them, we've been through a lot." When the Colonel has a gun to Caesar's head, trying to get him to tell the other apes to "get back to work" Lake lifts a rock above her head showing that she is ready to work, and thus saves his life when everyone begins to follow her.
She is shown taking care of Cornelius again after they break free, clinging to him when an avalanche almost covers the apes.