Something else that could be posing a problem for Sheldon is that with Raj taking his old room, it makes it that much more permanent that he lives with Amy now.
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?
