In season 1, episode 11 of The Big Bang Theory, “The Pancake Batter Anomaly,” Sheldon falls sick with a cold after a sick Penny pays a visit. He’s used to being babied by his mother when he’s ill. But ...
The episode starts off with Leonard Sheldon and Penny int heir apartment. Penny talks about how she got a role in Rent and has to sing for her part so she debutes her singing to Leonard and Sheldon.