Big Bang Theory, portrayed by actor Johnny Galecki. Leonard is an experimental physicist,

who shares an apartment with colleague and best friend Dr. Sheldon Cooper. For his portrayal,

Galecki was nominated for a Primetime Emmy Award and a Golden Globe Award in 2011.

Leonard has been described as the straight man of the series. Penny is Leonard's next-door

neighbor and main love interest, and the teasing of romance between the two of them is a major

force driving the series. In "The Gorilla Dissolution", they finally become engaged.

Creation and casting Leonard is named after actor/producer Sheldon

Leonard, and Nobel Prize Laureate Robert Hofstadter. Johnny Galecki was originally asked to play

the role of Sheldon Cooper, but thought he would be "better suited" for the character

of Leonard. Personality

Originally from New Jersey and a graduate of Princeton University, Leonard works as

a Caltech experimental physicist, mainly working with lasers, and shares an apartment with

colleague Sheldon Cooper in Pasadena, California. He is usually seen wearing his characteristic

black thick-framed glasses, low-cut black Converse All Stars sneakers, pastel hoodies

or neutral-colored sweat jackets or a combination of the two, brown or red trousers, and physics-themed

T-shirts. His various girlfriends have tried to change his outfits: Penny had no success

while Stephanie got him to wear dress shirts and sweaters, and Priya got him to briefly

switch to dress shirts, waistcoats and dark slacks; he reverted to his original outfits

after she leaves for India, but started eschewing his hoodies in favour of unbuttoned safari

shirts and non-hooded jackets towards the end of the seventh season, a trend that continued

into the eighth season. Although Leonard feels at home with his geek

colleagues, he wants to be more social. Among the main characters, he generally has the

least amount of difficulty interacting with "non-geek" individuals. He is instantly captivated

by Penny, and from the beginning sets out to date her.

In early episodes, Leonard is reluctant to let Penny know about his recreational activities,

as he does not want her to see him as a geek. While certainly a geek by most definitions,

he is less socially inept than Sheldon, Raj, and Howard.

Leonard can also play the cello, although he holds the bow upside down and plays on

the finger board. As seen in the season 1 episode "The Hamburger Postulate", he and

Leslie Winkle practice their instruments and then leave to have intercourse

Despite his attempts to not appear to be a geek, Leonard owns, among other things, Star

Wars hygiene products, a prop of the One Ring, an expansive Superman comic book collection

and a Battlestar Galactica Colonial warrior's flight suit. Early in the series, Leonard

tried to get rid of his collectables to impress Penny with his maturity. However, he changed

his mind when he saw that Penny was already dating another man.

Because he has lived with Sheldon for many years, Leonard knows him better than his other

colleagues: this has led Sheldon to believe that Leonard is his best friend. Nevertheless,

Leonard often finds himself explaining Sheldon's behavior or serving as a mediator between

him and other people in many situations. For instance, when Penny and Sheldon engaged in

a fierce dispute, Leonard gave Penny Sheldon's mother's phone number so she would call her

son and scold him for his behavior, thus ending the fight. "The Staircase Implementation"

features a flashback to when Leonard first moved in with Sheldon. Leonard explains to

Penny that he moved in despite the difficulty of living with Sheldon because the rent was

so reasonable. Shortly after moving in, during a rocketry experiment Leonard, Raj and Howard

conducted, Sheldon observed miscalculations Leonard made in mixing the rocket fuel and

managed to avert disaster by grabbing the fuel and placing it in their apartment building's

elevator. The resulting explosion disabled the elevator, thus explaining why the elevator

is out of order for the duration of the series. Leonard explains that Sheldon, despite his

tendency to alienate others, kept quiet about Leonard's destruction of the elevator.

Despite Leonard's reasonable nature and friendly personality, he occasionally demonstrates

a mean streak. These include deliberately triggering Sheldon's obsessive compulsive

problems, mocking Howard and Raj whenever they slip up, and making sniping comments

when Penny's commitment issues flare up. In addition, he is often shown to be quite jealous,

often feeling insecure and defensive whenever Penny interacts with another guy, and on one

occasion trying to frighten off a British college student she was doing a project with,

because Penny commented positively on his accent.

Leonard's primary health concern is his lactose intolerance: his consuming melon or any dairy

products results in flatulence. Leonard wears eyeglasses because of myopia, and cannot see

without them. On one occasion, when his glasses were broken at the movie theater, he had to

surreptitiously return to his apartment and retrieve his backup glasses. In order to avoid

detection by a sick Sheldon and Penny, who was nursing him, Howard and Raj helped him

to navigate through the living room by using a helmet camera. Leonard states in one episode

that he suffers from sleep apnea. During his relationship with Leslie Winkle, he tells

her that many members of his family have died from heart disease and thus he has a genetic

disposition to the condition. At various points in the show, Sheldon also

says that Leonard gets carsick unless he sits in the front seat. In season four, it was

revealed that Leonard has asthma as well, and also has to use the inhaler after intercourse.

Family All of the members of Leonard's family are

accomplished scientists, except for his younger brother Michael, who is a tenured law professor

at Harvard University. Leonard's mother, Dr. Beverly Hofstadter,

is a psychiatrist and neuroscientist. She has a personality almost identical to Sheldon's,

including strict speech patterns, lack of social conventions, and attention to detail,

and she is principally responsible for Leonard's difficult childhood. Sheldon and Beverly have

a friendly relationship where they share details of each other's lives with Sheldon often failing

to pass on significant information such as Leonard's parents divorcing and the family

dog Mitzy's death. Leonard is upset with that fact that she tells Sheldon more than she

tells him. After a night out of bonding and drinking with Penny, Beverly kisses Sheldon,

but realizes there are no romantic feelings involved.

Due to his mother's views, Leonard never celebrated his birthday when he was a child, and when

she visited him she was not impressed with his unoriginal research. Leonard revealed

to Penny that he built a "hugging machine" when he was young in order to compensate for

the lack of affection from his mother. He further stated that his father used to borrow

it. Beverly also belittles Leonard by pointing out that his brother and sister are more successful

in their respective fields than he is. Leonard's brother, Michael, is a Harvard law professor

and is engaged to the youngest appellate court judge in New Jersey history, and his older

sister is a cutting-edge medical researcher working with gibbons to cure diabetes. Leonard

also dislikes Christmas because instead of gifts the Hofstadter kids had to turn in papers

to "Santa" which were graded the next day and in the course of six years he never got

over a "C minus", which in Sheldon's view was a true gift, because, by Sheldon's thoughts,

he never deserved over it. Leonard had a childhood pet, a cat named Dr. Boots Hofstadter.

Leonard's father is briefly mentioned as an anthropologist. Sheldon reveals that Leonard's

middle name, "Leakey", comes from famed archaeologist Louis Leakey, with whom Leonard's father had

worked. Leonard is embarrassed by his middle name and its humorous connotations, and rarely

mentions it, as the name is an obvious embarrassment. Apparently his father was not very affectionate

towards him either, when he mentions that he had to compete with the bones of an Etruscan

kid for his father's favour. Though little is known about Leonard's extended

family, a few references to it have been made. In the first episode, Sheldon and Leonard

discuss Leonard's grandmother, who had visited them on Thanksgiving the year before. She

has Alzheimer's disease and apparently "had an episode" during her visit, which resulted

in her stripping off her clothes and carving the turkey. On Beverly's first visit, she

tells Leonard that his uncle Floyd has died, which greatly upsets him. Leonard also has

several other uncles, which Sheldon says are all very bald, and when they gather together,

they look "like a half carton of eggs." Leonard describes his aunt, however, as being "one

of the hairiest women you'll ever meet". Work

Leonard has an IQ of 173, and was 24 years old when he received his PhD from Princeton

University. Leonard also received a dissertation of the year award for his doctoral paper on

experimental particle physics. Leonard has been established to have been

a child prodigy, and a gifted scientist with an impressive knowledge of theoretical physics.

His work as an experimental physicist often includes the use of lasers, such as a helium–neon

laser or free-electron laser, and his research topics have varied from Bose–Einstein condensates

and foundations of quantum mechanics to soft cosmic rays at sea level and development of

novel rocket propellants. Leonard designs experiments in order to test theories but,

according to Sheldon, his work is mostly derivative and thus unimportant.

Although Leonard's attempts to disprove the existence of dark matter were made moot by

the work of another physicist, Leonard helped to solidify proof of the hypothetical matter's

existence with a photomultiplier, and was invited as keynote speaker to a topical conference

by the Institute of Experimental Physics for his successful research on super solids.

From the season 6 finale, The Bon Voyage Reaction" Leonard heads to the United Kingdom to work

on a physics project searching the hydrodynamics equivalent of the Unruh effect, sponsored

by Professor Stephen Hawking, for three months on a ship in the North Sea.

Relationships Leonard became interested in Penny almost

immediately after seeing her for the first time. His infatuation with Penny becomes the

major force that drives the series during the first seasons. By the end of the first

season, Leonard finally managed to ask Penny out, and they had their first date. Subsequently,

they broke up because Penny felt she was not as smart as Leonard would like.

Besides Penny, Leonard has been involved with only a few other women. One of Leonard's former

girlfriends that is mentioned in several occasions is Joyce Kim, who did not appear until the

third season. Leonard's friends recalled on many occasions that they were together for

only 27 days, after which Joyce, later revealed to be a spy, defected to North Korea.

Initially, after feeling that Penny was not for him, Leonard turned his attention to fellow

scientist Leslie Winkle. The first time Leonard asked Leslie out, she rejected him, and his

further relationships with her proved to be only short-lived casual sex encounters that

only happened to satisfy Leslie's libido. Leslie briefly started dating Leonard during

Season 2, but when he failed to back her up in an argument with Sheldon, she dumped him.

In the second season, Leonard began a stable relationship with a physician named Stephanie

Barnett. Although the relationship went well, even earning Sheldon's approval, Leonard felt

uncomfortable with Stephanie moving in with him, and the relationship ended.

On another occasion, when Leonard's mother was visiting, he and Penny came very close

to having sex, but Leonard ruined the moment by suggesting that they were burying their

lifelong issues with their parents by doing so, which offended Penny. In the second season

finale, when Leonard, Sheldon, Howard, and Raj were due to leave for a three-month scientific

expedition to the North Pole, Penny privately expressed sadness, and wish that he would

not leave. In the third season premiere, Leonard and

Penny finally started a romantic relationship and had intercourse for the first time. However,

the relationship ended after eight months, after Leonard told Penny he loved her and

took umbrage at her inability to reciprocate, which led to friction that was exploited by

guest star Wil Wheaton who appeared as a fictionalized version of himself, who observed and exacerbated

it in order to break them up in the middle of a bowling match Wheaton's team was having

against Leonard, Penny, Sheldon, Howard and Raj.

Shortly after his breakup with Penny, in "The Plimpton Stimulation", Leonard has a one-night

stand with Dr. Elizabeth Plimpton, a physicist he admires, when Sheldon invited her to stay

in their apartment for a brief visit. This encounter causes some tension between Leonard

and Penny, who is somewhat judgmental of Leonard's doing so. However, the two later resolve their

feelings and their friendship continues. In the third season finale, "The Lunar Excitation",

after Penny's failed attempts to move on from her relationship with Leonard, she becomes

intoxicated and has sex with him. In the morning, Leonard believes that their relationship has

resumed, though Penny tells him that the previous night was a mistake. This causes a strain

on their friendship; at the end of the episode, Leonard becomes intoxicated and tries to have

intercourse with her, prompting Penny to push him out of her apartment, to which Leonard

suspects a double standard. He immediately makes the same advances towards Leslie Winkle,

who replies 'Let me think about it" and slams the door in his face.

Throughout the fourth season, it becomes obvious that Penny is still in love with Leonard.

It is unclear whether or not Leonard has noticed this, though he clearly is still interested

in Penny. In "The Benefactor Factor", a woman propositions Leonard in exchange for a large

donation to the physics department; he initially resists and she admits that she planned to

make the donation anyway, after which they engage in a one-night stand. Leonard arrives

home the next morning, whereupon Penny recognizes his "walk of shame" and Sheldon thinks Leonard

has a future in becoming a gigolo to rich ladies in exchange for donations.

Leonard also has an affair with Raj's younger sister Priya, despite a pinky swear with Howard

that neither of them would attempt to make a move on her, and Raj giving his strong disapproval.

When Priya returns, she and Leonard begin a relationship. Raj strongly opposes this,

and Penny is secretly uncomfortable with Leonard dating someone else, eventually breaking down

and crying while talking with her friend Amy Farrah Fowler. Once again, Leonard is unaware

of Penny's true feelings. Subsequently, Priya pressures Leonard into ending his friendship

with Penny, which he attempts with extreme reluctance. Penny complies, though it is clear

that she does not want Leonard out of her life. Penny eventually resolves to stay in

Leonard's life by ingratiating herself to Priya.

In the Season 4 finale, Leonard runs into Penny and Raj as they come out of his room