Ramona Nowitzki is a postdoctoral researcher and former graduate student of Caltech who is a huge fan of Sheldon's work and has a crush on him. A former Olympic swimmer, she helped Sheldon calculate the masses of all the fermions in his paper reconciling the black hole information paradox with his theory of string network condensates. Prior to her return to Caltech, she performed analysis of LHC signatures of scalar dark energy at CERN for her first postdoctoral fellowship.
She meets Sheldon personally in the cafeteria and arranges to have dinner with him in his apartment. Where other people might be worried about such behavior being reminiscent of stalking, Sheldon reacts positively to Ramona by appreciating the fact that he's getting a free dinner. During their date, the rest of the gang is sitting on the couch as spectators of this strange turn of events until she implies that they should leave.
She keeps "helping" Sheldon by arranging suitable working conditions for him, such as getting breakfast for him at the cafeteria and giving caring for his feet. Unfortunately for Sheldon, she overdoes her insistence that Sheldon dedicate his time solely for work, depriving him of his favorite hobbies such as playing games, watching TV, and going for paintball with the guys. Even more unfortunately for Sheldon, he can't seem to get rid of her, especially when she settles herself in his apartment (on the couch). At times, she appears very suddenly and stalks around the apartment staring at people like the T-X terminator from Terminator 3: Rise of the Machines.
Ramona proves to be irritating for the entire group, especially when she assumes that Penny likes Sheldon. She still asks Penny to be sisters with her. She makes it difficult for anyone to communicate with him and scares them away.
Eventually, Sheldon solves the problem he's been working on. Enthusiastic about his solution, he asks Ramona how he can reward her for all her help. When she asks for him to share credit with her and name the theorem "Cooper-Nowitzki", he finally kicks her out of the apartment. Ramona leaves passing by Penny, who asks if they are still "sisters'. ("The Cooper-Nowitzki Theorem")
She reappeared in the Season 10 finale "The Long Distance Dissonance", hanging around Sheldon while Amy is away at Princeton University. By this time Ramona had her PhD. It turns out that despite seeing his true colors earlier, she never stopped having feelings for him. The gang becomes worried for Sheldon when she begins chasing him again. Ramona eats with him, goes swimming with Sheldon and visits with the gang in apartment 4A. Sheldon was told by Penny of her romantic interest in him and seems to finally understand. At lunch, Sheldon asks her if she has a romantic interest in him, she asks him "What if I do?" and then kisses him. Sheldon is shocked and then immediately flies to New Jersey to propose to Amy.
She reappeared in the Season 11 premiere, "The Proposal Proposal" where Raj asked her out again, but she declined. Raj tells her about Sheldon and Amy's engagement which she already knew about. She appears in the final scene where Amy comes up to her and the guys expect a fight between the girls for Ramona kissing Sheldon. Instead Amy thanks her for getting them engaged and hugs her, with a confused Ramona patting Amy with a nervous smile.
- Actress Riki Lindhome is half of the comedy musical duo Garfunkel and Oates. Her musical partner in the duo is fellow actor Kate Micucci, who portrayed Raj's ex-girlfriend Lucy. They also wrote the song that Howard sang to Bernadette in "The Romance Resonance".
- Ramona had the biggest crush on Sheldon until Amy appeared.
- Ramona was once an Olympic swimmer.
- Unlike Amy, Ramona is the only woman besides Sheldon's mother who can tame or control him.
- Ramona first appeared in "The Cooper-Nowitzki Theorem" (S2E6) and then reappeared in "The Long Distance Dissonance" (S10E24), a span of 208 episodes; this was the longest for any character on The Big Bang Theory.
- It is unknown if she is going to stop pursuing Sheldon after he married Amy though appears aloof when Sheldon returns from New Jersey.
- Raj even asked her out twice and she refused. She is happy with Amy and Sheldon getting engaged. Amy thanked her for getting them together, but it is unknown if Ramona is genuinely happy with the engagement.
- When Mary Cooper learned of Ramona, she was shocked to hear another woman was interested in Sheldon.
- Sheldon's sister Missy had the greatest break between appearances on the show with a ten-year gap for fictional characters. Ramona Nowitzki was second with a nine-year gap between appearances. Leslie Winkle has a six-year gap between appearances. Real scientist George Smoot had a ten-year gap between appearances.