The house of Dr. Gerhart appears in House Calls. It is possessed by the music Gerhart used to bring his house to life just so he could have a friend. Gerhart refers to his house as a she, meaning his house is a female, which can be concluded as the house makes woman-like groans. The house is very jealous of anyone who comes between her and her owner, Gerhart. Which is why it became immediately jealous of courage, Muriel and Eustace. And then attacked their farmhouse by throwing bricks and wood at their home. The house is later calmed down when Courage and Gerhart decide to redecorate it by painting it pink and cleaning the insides. After that, the house became good and peaceful rather than jealous and cruel.
This house seems reminiscent of the house from Monster house, where a man's wife died while their house was being made and her body was part of the foundation. Her soul became entrapped inside the house and the man stayed out of love for his wife and to protect others from the house, who attacked those that came by. Unlike Gerhart's house, the house in Monster House never calmed down, remaining hateful of others including children.