Crazy Aunt Gretchen.
Crazy Aunt Gretchen was Filburt's crazy aunt, who told him that if he ever touched one piece of candy, the Hopping Hessian would take him away. She appeared for a couple seconds in "The Big Answer", which was her only speaking role (voiced by Linda Wallem).
Gretchen is considered crazy for never leaving her tank in her youth; resulting on her having to modify it when she got too big to move.
She makes a brief appearance in Rocko's Modern Life: Static Cling where she is seen talking to Gordon, when Heffer and Filburt accidentally toss their smartphone into her tank while they fight over it, she is then electrocuted and falls over dead.