Christy is a former friend of Penny from Nebraska who was engaged to Penny’s cousin while sleeping with Penny’s brother Randall. Penny thinks of her as a family member and lets her stay with her for a short time.
Christy hooks up with Howard in Penny’s room and drives Penny out of her own apartment. Christy is very materialistic, and she goes out with Howard under the condition that he buys her stuff. After confronting Howard’s mother, who threatens to take Howard out of his will if they keep dating, she dumps him.
Valerie Azlynn as Alicia – Then
Alicia is Leonard, Penny, and Sheldon’s former neighbor who lives in the apartment above them. She first meets Leonard and Sheldon in the lobby, where Sheldon bombards her with annoying questions. Annoyed, Alicia nonetheless answers every question, and Sheldon accepts her.
Leonard, Howard, and Raj swoon over her, doing her many favors. Penny is annoyed that Alicia is taking advantage of the boys and jealous. Penny tells the boys that Alicia is using them. The two get into a quarrel after Penny confronts Alicia about this, resulting in Penny’s black eye and the boys stopping to do things for Alicia.
Valerie Azlynn as Alicia – Now
Valerie has been acting long before her gig on TBBT. She played the role of Damien’s assistant in the comedy "Tropic Thunder," along with Ben Stiller.
In 2012 she played Melanie Sutton in the series "Sullivan & Son." Today, she continues to play small roles in TV series and films.
Brooke D’Orsay as Christy Vanderbel – Now
Brooke has acted in multiple series since her role as Christy in TBBT. She acted as Heather Hanson in the comedy series "Happy Hour." She also was in an episode of "How I Met Your Mother." She was the voice of Caitlin in the animated series "6Teen" for 86 episodes.
She played two different characters in "Two and a Half Men" — in 2007, she played Robin, and in 2014, she played Kate. Later, she played the role of Paige Collins in the show "Royal Pains." Her last two gigs were minor parts in TV movies.
Riki Lindhome as Ramona Nowitzki – Then
Ramona works at Caltech as a postdoctoral researcher and is a big fan of Sheldon and his work. She meets him in the cafeteria, and they arrange to have dinner at his apartment.
His friends feel that she is a bit obsessive, but Sheldon just appreciates that he’s getting free dinner. During their date, the rest of the gang sits on the couch as onlookers of this strange turn of events. Eventually, Sheldon solves the problem that he’s working on, and Ramona wants to share credit for it. He reacts by kicking her out of the apartment.