The is a spin on "Rags to Riches", which refers to a person who rises from poverty to wealth or fame; it is a literary theme used by writers such as Horatio Alger.
The will being read to Droopy and Spike is signed "W. Higgins". This refers to Bill Higgins, who was an assistant animator but never received screen credit for his work on MGM cartoons.
The mansion is appointed with the finest in luxury goods, including a modern postwar kitchen. However, it appears to be powered by natural gas. This was not unusual at the time, as the transition to electric energy for all consumers happened during the mid century era.