In the episode when they're on the ship leaving for Paris (don't remember the name), the gang is in their cabin on the ship with Lucy's mother. Lucy tells her mother to cable her if the baby sneezes, her mother tells her to get her a bottle of French perfume, etc. Somewhere in there, Lucy calls her mother Mrs. Trumbull (sp?), the lady in their apartment building who babysits little Ricky . . .