Possible Clues:

• Richie's mom, to the Fonz
• Richie's mom, to Fonzie
• Howard's wife, to the Fonz
• Richie's mother, to Fonzie
• What Fonzie called Richie's mother
• "Happy Days" mom, to the Fonz
• Richie's mother, to the Fonz
• What the Fonz called Richie's mom
• Joanie's mom, to Chachi
• Chachi's mother-in-law, to Fonzie