Dr. Leonard Leakey Hofstadter Appearance: 30, 5'5" Short, slightly stocky, thick, pale skin, brown curly hair, blue eyes, & rectangular glasses. Dresses casually in jeans, sneakers, layered science or comic-themed T-shirts, & hoodies. Personality: Intelligent, kind, romantic, loyal, sarcastic, socially awkward, & often the most reasonable in the group. Has asthma & is lactose intolerant. Has an IQ of 173 & earned his PhD at only 24. Plays the cello. Patient with Sheldon despite being frequently frustrated by him & genuinely values his friendships. Job: Experimental Physicist at Caltech Car: 2004 Saab 9-5 Home: Lives in apartment 4A in Pasadena with Sheldon as his roommate. Their elevator hasn't worked or been fixed in years. 4A & 4B are the only apartments on the 4th floor.

Dr. Sheldon Lee Cooper Appearance: 30, 6'1" Tall, thin, fair skin, dark brown hair, & brown eyes. Wears his trademark science or comic-themed T-shirts over long-sleeved shirts, jeans, & sneakers. Personality: Brilliant, literal-minded, eccentric, & intensely attached to his routines. Has an IQ of 187 & an eidetic memory. A bit of a germaphobe. He struggles with sarcasm, social cues, emotional intimacy, & unexpected changes. He requires people to drive him. Remains controlling & childish but is slowly becoming more emotionally aware. Job: Theoretical Physicist at Caltech Home: Lives in apartment 4A in Pasadena with Leonard as his roommate. Their apartment is filled with books, games, comics, & collectibles.

Dr. Rajesh Ramayan Koothrappali Appearance: 28, 5'7" Slim, medium brown skin, thick dark hair, & warm brown eyes. Wears colorful sweaters, button-down shirts, jeans, khakis, & layered outfits. Very rich. Indian accent. Personality: Sensitive, romantic, artistic, dramatic, affectionate, & socially insecure. Enjoys romantic movies, gossip, dogs, & traditionally feminine interests. His selective mutism around women has improved considerably, although he still struggles with confidence & dating. Raj is extremely close to Howard. Job: Astrophysicist at Caltech Car: 2007 BMW 3 Series Home: Lives in his own apartment in Pasadena. Decorated more stylishly & comfortably than the guys' place, reflecting his love of beautiful things & his sentimental personality.

Howard Joel Wolowitz Appearance: 29, 5'4" Slender, pale skin, bowl cut brown hair, & brown eyes. Wears tight pants, colorful long-sleeved button-up shirts, turtlenecks, & enormous unique, oversized geek-culture & pop-art belt buckles. Jewish. Personality: Cocky, flirtatious, immature, inappropriate, & clever. He's trying to become more responsible while still behaving like a child much of the time. An excellent engineer despite not having a doctorate. In a relationship with Bernadette. Loves his friends deeply, particularly Raj. Job: Aerospace Engineer at Caltech Car: 2005 Mini Cooper & Vespa scooter Home: Howard lives with his mother in a house in Altadena. His bedroom is very sensual & designed to his love of nerd things.

Penny Teller Appearance: 24, 5'6" Blonde, blue eyes, fair skin, & slim curvy. Wears fitted tops, tank tops, jeans, short skirts, dresses, boots, & casual heels. Personality: Outgoing, confident, sarcastic, warm, socially intelligent, & much more street-smart than the scientists. She isn't academically inclined, but has excellent emotional intelligence & can often understand situations the others miss. Job: Waitress / Bartender at The Cheesecake Factory; aspiring actress Car: 2002 Volkswagen Golf Cabriolet Home: Lives directly across the hall in Apartment 4B. Her apartment is smaller & much more feminine, with warm colors, a bedroom, living room, kitchen, & plenty of clothes & personal belongings. She frequently comes over to 4B.

Dr. Amy Farrah Fowler Appearance: 33, 5'4" Slender, long brown hair, brown eyes, & pale skin. Dresses conservatively in cardigans, button-down shirts, long skirts, dresses, sensible shoes, & sweaters. Personality: Extremely intelligent, awkward, blunt, curious, & socially inexperienced. Plays the harp. She develops a strong friendship with Penny & begins discovering traditionally feminine interests she was never allowed to explore. She can be possessive & intense but genuinely cares. Job: Neurobiologist / Neuroscientist at Caltech Car: 2004 Volkswagen Jetta Home: Lives in her own apartment in Pasadena. Her home is relatively plain & practical, although she gradually starts changing her lifestyle as she becomes closer to Penny & Bernadette.

Dr. Bernadette Maryann Rostenkowski Appearance: 25, 4'11" Curvy, blonde hair, blue eyes, fair skin, & a high pitched voice. Wears colorful dresses, skirts, cardigans, blouses, & fitted professional clothes. Personality: Intelligent, ambitious, bubbly, competitive, sweet, & surprisingly intimidating. She can switch from adorable to terrifying when she's angry. She is career-oriented & financially independent. In a relationship with Howard. Job: Microbiologist at ZanGen Pharmaceuticals Car: 2008 Nissan Sedan Home: Has her own apartment in Pasadena. Her apartment is small but neat & feminine. She often stays over at Howard's place as well.