The surname of Leonard and his family: Alfred, Beverly, Michael, and a sister whose name has not been confirmed.
Season 1, Episode 9 - The Cooper-Hofstadter Polarization
Aired March 17, 2008
When Sheldon and Leonard are asked to present their work at a physics conference, Sheldon unilaterally decides not to. Leonard and Sheldon feud when Leonard decides to present their work alone in spite of Sheldon's objections. Penny's attempts at reconciling the pair only make matters worse.
Season 2, Episode 20 - The Hofstadter Isotope
Aired April 13, 2009
When Penny accompanies the guys to the comic book store, she is charmed by store owner Stuart and agrees to go on a date with him. Leonard wonders why Penny has fallen for a guy who is just as geeky as he is. In an effort to improve his love life, Leonard ventures out to Ladies' Night with Howard and Raj.
Season 7, Episode 1 - The Hofstadter Insufficiency
Aired September 26, 2013
With Leonard still away at sea, Sheldon and Penny bond by sharing some intimate secrets. Meanwhile, still recovering from his break-up from Lucy, Raj tries to get back on the dating scence. Elsewhere, Amy and Bernadette attend a biology convention together.