The Zoo is where Roger tries to meet with Stan to request that he'll let him move back into the house without Andy Dick around in "You Debt Your Life".
When Francine finds Roger living in a YMCA after a fight with Stan, she suggests Roger try to remind Stan of all the good times they had together and Roger decides to try to meet with Stan at the zoo without Andy around after Stan replaces Roger. Stan meets Roger at the zoo but has brought Andy with him, spoiling Roger's chance. When Roger comes to the conclusion that he needs to save Stan's life so he'll owe him a life debt again, he pushes Stan into the polar bear enclosure. However, Roger and Andy fight over rescuing Stan and the polar bear eats Stan's legs.