Sheldon has also admitted that he considers Penny to be his friend.A number of episodes depict Penny's assimilation of nerd culture through her relationship with the men, and has developed to quote some science fiction shows (like Star Trek), and movies (Star Wars).In the fifth-season episode "The Speckerman Recurrence", it is revealed that Penny was a bully during her time at school.
In "The Intimacy Acceleration", Sheldon asks her, "If you could wake up tomorrow having a gained any one quality or ability, what would it be? In one episode, Sheldon tries to "improve" Penny, rewarding her with chocolate for what he considers "correct behavior", as in operant conditioning of lab rats.
" Penny replied, “Well, not to steal from the Bible, but turning water into wine sounds pretty good.”. Leonard noticed it and accused Sheldon of modifying her like Pavlov's dogs.
In return, Sheldon gives Penny several baskets of bath products and then a long hug, to both her and Leonard's surprise.
When Sheldon's World of Warcraft account is hacked and the four men all back down from the much larger hacker who also steals Sheldon's Klingon Bat'leth, Penny kicks the hacker in the groin.
Leonard has likened her to The Hulk when she gets angry, When her car's engine finally fails in Season 7, Leonard buys her a new one so she can go to auditions and pursue her dream of becoming an actress.