: A sex-crazed aerospace engineer with an overbearing mother. Rajesh Koothrappali (Kunal Nayyar)

: A socially awkward experimental physicist who falls in love with Penny instantly.

The first season introduces the central dynamic that would carry the show for 12 years: high-IQ physicists Leonard and Sheldon's awkward attempts to navigate "normal" life after an aspiring actress named Penny moves in across the hall. Sheldon Cooper