He does have a softer side, as he does care about his friends, and loves his mom, grandma, and girlfriend Amy, though he often insults them either about their intellect levels or different opinions.
He shares an apartment in Pasadena with friend and fellow physicist Dr. Sheldon has a deep love and interest for science fiction and comic books, to the point of an obsession, and shows particular affinity for Spock, a fictional character from the Star Trek franchise.
A running gag has him always knocking on doors in a pattern of three knocks and one call repeated three times, which he has the urge to complete no matter what.
Sheldon has a superiority complex and makes no effort to hide his contempt for other people's lower intellects, often making highly inappropriate comments.
In season, after Sheldon moves in with Amy, Leonard and Penny have apartment 4A to themselves.