"The Desperation Emanation" (Season 4, Episode 5) of The Big Bang Theory focuses on Leonard’s insecurity as the only single member of the group and Sheldon’s panic over escalating his relationship with Amy. Notably, this episode marks the first appearance of Amy's mother via Skype and is the first in the series without Penny. For more details, visit Big Bang Theory Wiki . The Desperation Emanation | The Big Bang Theory Wiki