He was portrayed by Jason Alexander, who also voiced Abis Mal.
In some ways, it is bordering on glorification of evil.
In one scene, he literally murders Neil, because he stole his girl, by cutting his life cord.
Costanza is not a mean guy. But he can outright turn into a monster if you screw him over. He is a game-player though. Strangely enough game-playing tends to be a way of many, like Rocco Klein in Clockers.
In one scene, he plots revenge on his boss for calling him a loser (in "The Revenge").
It's important to note that Costanza didn't start off this way, but became more evil as the series progressed. Though less than heroic George does show signs of being a genuine protagonist.
George is neurotic, self-loathing and dominated by his parents, yet also prone to occasional periods of overconfidence that invariably arise at the worst possible time. Throughout Seinfeld's first season, George is depicted as moderately intelligent – at one point, he mentions an intellectual interest in the Civil War and, in some early episodes, appears almost as a mentor to Jerry – but becomes less sophisticated, to the point of being too lazy even to read a ninety-page book (Breakfast at Tiffany's), preferring to watch the movie adaptation at a stranger's house instead. However, one Chicago Tribune reviewer noted that, despite all his shortcomings, George is "pretty content with himself".
George exhibits a number of negative character traits, among them dishonesty, insecurity and neurosis, many of which seem to stem from a dysfunctional childhood with his squabbling parents Frank and Estelle, and often form the basis of his involvement in various plots, schemes and awkward social encounters. George's relationship with Frank is estranged. Episode plots frequently feature George manufacturing elaborate deceptions at work or in his relationships in order to gain or maintain some small or imagined advantage or (pretend) image of success. He had success in "The Opposite", where he starts (with Jerry's encouragement) to do the complete opposite of what his instincts tell him to do, which results in him getting a girlfriend and job with the New York Yankees. His neurosis is also evident in "The Note", where he begins doubting his sexuality after receiving a massage from a male masseuse.
George sometimes refers to himself in the third person (for example, "George is getting UPSET!"), after befriending a person with a similar trait in "The Jimmy".
George's occasional impulsiveness often gets him into trouble, like when he flees a burning kitchen, knocking over several children and an old woman in the process, so he could escape first during his girlfriend's son's birthday party in "The Fire". However, there are moments where George exhibits remarkable courage, but usually accidentally and often in support of inane lies he'd rather not confess to. For instance, in "The Marine Biologist", he goes into the sea alone to save a beached whale because his date, a woman on whom he had a crush in college, thinks he's a marine biologist and even tells her the truth about his occupation after he saves the day. However, this causes her to reject him immediately, and he's forced to take the bus home.
George often goes to impressive measures to build and maintain his relationships with women. In “The Conversion”, he goes through the process of converting to the Latvian Orthodox religion as his girlfriend’s conservative parents wouldn't let her date somebody outside their religion. In “The Susie”, he deems it so important that he make a grand entrance at his work’s ball with his attractive girlfriend Allison that, upon finding out that she plans to break up with him, George goes to great lengths to avoid her before the ball, stating "If she can't find me, she can't break up with me.” Ultimately though, the one relationship he holds long-term, with his fiancé Susan, is the one about which he's seemingly least enthusiastic, as shown by his ongoing attempts to first postpone, and later cancel, their wedding and his rather calm reaction when she suddenly dies. In fact, in "The Foundation", George shows greater emotion while discussing the death of the Star Trek character, Spock, in the movie, "The Wrath of Khan" than after Susan's death.
In some episodes, George aligns with both Kramer and Elaine in some episodes, against whom he's also frequently pitted. With Elaine, while he gets into arguments with her, they also work together, most notably in "The Cadillac", although George states in "The Dinner Party" that he's frightened of Elaine. George and Kramer usually feel awkward around one another but working together (and against one another) in "The Busboy", "The Stall" and "The Slicer". "The Susie" is the only episode where their relationship is as prominent as the relationships between the other characters. Some episodes, like "The Raincoats", "The Money", "The Doorman" and "The Fusilli Jerry", would suggest that Kramer has a more comfortable rapport with George's parents than George.
He has an interest in nice restrooms and his personal bathroom habits that borders on obsession. In "The Revenge", he quits his real estate job solely because he's forbidden to use his boss' private bathroom. In "The Voice", he admits that one of the reasons he's staying at a job his boss has asked that he resign from (for feigning a disability) is that it gives him "private access to one of the great handicapped toilets in the city". In "The Busboy", he claims to have an encyclopedic knowledge of the locations of the best public bathrooms in the city. He proves this in "The Bizarro Jerry" when he directs Kramer to "the best bathroom in midtown" at the offices of Brand/Leland, even describing the layout, marble, high ceiling and toilets that flush "like a jet engine". In "The Gymnast", he told Jerry that he always removes his shirt when using the bathroom because "it frees me up... no encumbrances". It's unclear if he dropped this habit after an embarrassing incident where he walked out of a bathroom shirtless at a lunch party attended by his girlfriend, her mom and other female members of her family. When working for the Yankees, he suggested having the bathroom stall doors stretched all the way to the ground (letting people's legs not be seen while in the stalls), and, in many episodes, he shows a fascination with toilet paper and its history. He also displays a fear of diseases, like lupus and cancer. In "The Wife", George gets into trouble for peeing in the shower at a gym but defends his action with, "It's all pipes! What's the difference?" even threatening to call a plumber to back him up.
Although occasionally referred to as dumb by his friends, many signs point to the fact that George is actually quite intelligent despite his neurotic behavior. George's foolishness is displayed in "The Cafe", where he has Elaine take an IQ test for him. Apparently, George's neurotic stupidity would progress until it became one of his primary characteristics. By "The Couch", he couldn't even concentrate enough to read a ninety-page book (Breakfast at Tiffany's). In "The Abstinence", it's discovered that George actually has what'd appear to be genius-level intelligence but can never access it because his mind is always so completely focused on sex. When circumstances let him temporarily remove sex from his mind, he's able to reach his true intellectual potential, solving a Rubik's Cube, answering a string of questions on Jeopardy! and giving Derek Jeter and Bernie Williams pointers on hitting based on Newtonian physics.
George and Jerry have been best friends since meeting in high school gym class. The extreme closeness of their friendship is occasionally mistaken for gayness. "The Outing" deals with a reporter from a New York University college paper mistaking George and Jerry for a gay couple, and, in "The Cartoon", George dates somebody who Kramer insists is merely a "female Jerry". When George is forced to note to himself that the idea of a female Jerry who he can have a close personal and also sexual relationship with would be everything he's ever wanted, George, in horror, breaks off his relationship with the woman.