More on Sauce to the Goose is Sauce to the Gander from Infoplease:

• Sauce to the Goose is Sauce to the Gander - Sauce to the Goose is Sauce to the Gander (See Gander.) Source: Dictionary of Phrase and Fable, E. ...
• Gander - Gander (g hard). What's sauce for the goose is sauce for the gander. Both must be treated ...
• Dictionary of Phrase and Fable: S - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "S"