Amy asks Sheldon if they are ever going to have an intimate relationship and then they end up playing private D&D.
The girls join in on a game of Dungeons and Dragons for the very first time on The Big Bang Theory. "The Love Spell Potential" is the 23rd episode of the show's sixth season.

The Big Bang Theory Season 6 Episode 23 Quotes

Leonard: Sometimes change is good. You were worried about Zachary Quinto being the new Spock, but you ended up liking him.
Sheldon: Leonard, please, every time the topic of change comes up you throw Zachary Quinto in my face. I'm upset the mailman has a new haircut -- Zachary Quinto. I'm upset daylight savings time started -- Zachary Quinto. I'm upset daylight savings time ended -- Zachary Quinto. I'm saying this for the last time. Zachary Quinto was a weird, wonderful, unrepeatable event, so stop using him against me.

We have a new rule if no one talks for three minutes you can just hang up. I'm so into her.