Leonard's mother (played by Christine Baranski), a brilliant neuroscientist who has no concept of appropriate human interaction or warmth, comes for a visit. During her stay, she manages to alienate and cause emotional turmoil in everyone's lives except for Sheldon who is taken by her since they are so much alike. Leonard is not in the least happy with her presence and Penny feels likewise after his mother makes Penny explore and question her relationship with her father; both Penny and Leonard turn to each other and a bottle of tequila for comfort which leads them to explore much more than their individual childhood issues.
