While Sheldon is probably the first character that comes to mind when The Big Bang Theory is mentioned, it's Leonard who was originally framed as the show's main character - so we think it's fitting to start with him. Leonard is a talented experimental physicist with very nerdy leanings: he loves video games, comics and D&D. The series starts when Leonard, who has Sheldon Cooper as a roommate, falls desperately in love with beautiful neighbor Penny. Leonard has a good understanding of social norms and behaviours, but his friends' and roomate's actions constantly get in the way of him tryin to live the life he wants.
The role of Leonard is not the first one for Galecki, but it is the biggest one he's ever had. While today, Galecki is best known for his portrayal of Leonard, he first started out with another extremely popular sitcom: Roseanne!
Galecki played David Healy for the first 5 seasons of the show - but his role there was eclipsed by TBBT. Galecki's salary grew with the TBBT's popularity, and he's currently earning around $1 million per episode - one of the highest TV actor salaries in history.
Alessandra plays Claire, a cute bartender who asks Raj for help with the science fiction movie she's writing. Raj helps her out and falls for her in the process, ending up dating her….and Emily Sweeny, a macabre dermatologist who likes "cutting thing" - at the same time. Raj is torn about two-timing both of these women, and after a long, torturous bout of self flagellation, he decides to break up with them both.
Alessandra Torresani is no stranger to television - she even landed a lead role in another geeky TV show - the Battlestar Galactica science fiction spinoff series, Caprica. Other than her role in The Big Bang Theory, she had a string of appearances in other succesful TV shows, including Two and a Half Men, Husbands and American Horror Story. It seems like Torresani's star is on the rise, and she recently starred in Netflix's comedy movie, Step Sisters.
Stephanie first appears in the show’s second season as a doctor at a hospital Howard visits. Howard tries to seduce her by taking her to his workplace, where he lets her drive the Mars Rover around - but when she accidentally drives the Rover into a ditch, Howard freaks out and asks Leonard to drive her home. Unfortunately for everyone, Leonard and Stephanie end up hooking up in Leonard's car, and Stephanie and Leonard enter a comitted relationship far too quickly.
Johnny Galecki isn't the only Roseanne alum on The Big Bang Theory. When she was a kid, Sara Rue played a very young Roseanne on the show, in a scene depicting Roseanne's first meeting with Dan at a dance. Since leaving TBBT, she's appeared in guest roles in many other television shows; We’ve seen her as Brenda in Rules of Engagement, Kim Sallinger in Malibu Country and Candice in Mom. As of 2018, she can be seen in a recurring role on Netflix's A Series of Unfortunate Events.
Most fans agree that Leslie is Leonard's female version. She works in the same experimental physics department as him, wears the same thick glasses and generally displays similar behavior and attitudes towards many subjects. Still, where Leonard is kind hearted, Leslie often seems to be cynical and cruel, and while they both date, (and Howard finds himself in a relationship with her, too!) Leslie eventually ends up as season 2's main villian.
Still, over the years, things seem to have mellowed out, and in season 9 Leslie even comes to Sheldon's birthday party.
Johnny Galecki and Sara Rue aren't the only former Roseanne cast members to make it to The Big Bang Theory - or even the best known ones. Sara Gilbert is perhaps stil best known for her portrayal of Darlene Conner on Roseanne - and when the Roseanne was rebooted, she actually became the show's executive producer, alongside playing her old, well loved character.
Gilbert and Galecki used to date when they were teens, but following their relationship, Gilbert found out she was a lesbian, and has become an outspoken advocate for LGBTQ rights.
At the beginning of the show, Howard lives with his overprotective - and overbearing - mother, and works as an aerospace engineer at Caltech. Howard is the only one in the group who hasn't earned a doctoral degree, but rather "only" has a Master's. Still, his professional achievements are formidable. Despite this, his behavior is often quite creepy, especially towards women. In the third season, he meets Bernadette, who manages to tone his behavior down and ultimately becomes his wife and the mother of his children.
Simon Helberg has been appearing on film and television since the late 1990s, but The Big Bang Theory was his first big break. His appearance on the show has garnered him a Critics' Choice Television Award for Best Supporting Actor in a Comedy Series, and his appearance on the film Florence Foster Jenkins along with Meryl Streep and Hugh Grant has earned him a Golden Globe Award nomination. But perhaps most importantly, he provided the voice for Bian Zao in Kung Fu Panda.
