What made Greg decide to add Angela to the regular cast?
The idea that one of the gargoyle eggs from Wyvern was the child of Goliath and Demona came up way back in the first episode. The idea for their daughter and the name Angela came up early in the second season planning. The decision to add her was primarily to have a female in the cast, though other benefits (a mate for one of the Trio, the connection with Demona) didn’t occur until some time later.