Gretel Doofenshmirtz was Heinz Doofenshmirtz's great-grandmother who was a great cook, specifically in creating a meatloaf recipe with the secret ingredient of hate, as opposed to the usual secret ingredient of love (the reasoning for which is that, according to Heinz, Great-Grandma Gretel had some "issues"). She passed it onto her son: José Doofenshmirtz who passed it on to Mrs. Doofenshmirtz who passed it onto Roger Doofenshmirtz. Heinz then stole it ("Meatloaf Surprise").
