Roger the alligator (whom the penguins had previously met in the episode "Haunted Habitat") comes up to the penguins’ HQ when The Rat King and his minions invade Roger’s home and throw him out. Roger tells the penguins that he had tried being nice to the rats, including making muffins for them, but his efforts were not successful and that he is not comfortable with being aggressive to get his home back. Soon after Roger tries again to be nice to the rats and again gets beaten up by them, the penguins decide to help Roger confront the rats. When training Roger fails to be a viable option, Kowalski rigs up a contraption with a blender to switch Roger and Rico’s brains (not a physical transfer, but one done through the aid of the contraption) so that Rico, inside Roger’s body, could take care of the rats. Unfortunately, after defeating the rats, “Rico” begins to go on a rampage, tearing apart the zoo and the vicinity thereof. (Kowalski attributes this to the differential between an alligator’s cold blood and a penguin’s warm blood.) The penguins and “Roger” then try to stop “Rico,” who is eventually brought down when “Roger” sings, in a Jack Haley-style singing voice. At the end of the episode, once Roger and Rico had assumed their proper bodies again, Roger conducts the penguins in singing a lullaby. (subfactory.fr)