Mrs. Hofstadter (guest star Christine Baranski) meets Penny on the way up to Leonard's apartment and has no problem analyzing her and figuring out all her father issues.
Sheldon: I'll have a diet Coke. Penny: Can you please order a cocktail? I need to practice mixing drinks. Sheldon: Fine... I'll have a virgin Cuba Libre. Penny: That's... rum and Coke without the rum. Sheldon: Yes, and would you make it diet?