The Danvers Asylum for the Criminally Insane, known as Batshit Island, is where Dennis, Roger's old ventriloquist act partner is sentenced after Roger goes psychotic and kills the cast of Hollywood Squares in "The Talented Mr. Dingleberry".
When Steve tries to come up with an idea for a school talent show act after his singing is sabotaged, Roger pitches becoming his ventriloquist dummy. He shows off a scrapbook of his former act. Later, when Roger turns more psychotic than usual, Steve discovers that the scrapbook also contains clippings from where Dennis was blamed for a series of murders and sent away to the Danvers Asylum for the Criminally Insane. There, he finds Dennis who reassures him that it was indeed Roger who committed the murders, but in his rantings, also provides Steve with a clue as to the source of Roger's own psychosis.