Hayley had a non-speaking cameo appearance in "Foreign Affairs".
The entire Smith family from American Dad appear as part of a cold-opening for "Bigfat", with the scenes that were originally intended for "April in Quahog". When the Griffins greet their new neighbors, the Smiths, who moved into Cleveland's old house, Peter sees Roger. Stan tries to keep Peter quiet but is forced to have to kill him as he starts to tell Quagmire about the alien. The entire opening turns out to be a dream by Hank Hill.