The character is Archie Bunker without the knowledge of what he's doing. He has the mind of a child, basically, and a source of big laughs is when he doesn't realize he's doing something inappropriate.
Peter appears to be unintelligent and consistently depicted as crude and lowbrow. He enjoys activities such as going to up-market tailors and farting in Meg's cereal. His favorite pastime is watching TV. A running gag on the show is Peter's preference for Pauly Shore movies over classic films such as The Godfather and Citizen Kane. He is also a huge Kiss fan and followed them during the KissStock shows and even got a copy of Kiss Saves Santa for Christmas. Peter is also a huge fan of Barry Manilow, though this is a fact he has been known to deny in public (to a certain extent, anyway). Despite his love of these musicians, Peter's favorite song ever, told by Peter in the episode I Dream of Jesus, is Surfin' Bird by The Trashmen (and after aquiring the record from a 1950's themed restaurant, he annoys the whole family by playing it non-stop until Stewie and Brian steal it).Peter also mentions in an episode that he wears the male deodorant Speed Stick to his wife Lois quoting, "Smell my Speed Stick?" while he is rubbing her shoulders and trying to convince her to have sex with him in his office at the brewery.
An I.Q. test confirms that his low intellect places him in a category below mentally retarded, but above Creationists. His mental shortcomings have resulted in various accidents and deaths to other people; most notably to his surrogate father Francis Griffin, and on multiple occasions, his wife Lois Griffin. His attention span is also incredibly short; when he discovers his mental retardation in "Petarded", he closes his eyes while driving, wishing "it would all be over" (hitting Tom Tucker with his car instead).
Peter also has a habit for proving his masculinity, not wanting Lois to fall for another man. He is incredibly jealous of other attractions Lois has in her life, an attitude that tends to get out of hand in most cases; in "Stuck Together, Torn Apart", he goes so far as to punch his reflection in the mirror after Lois comments on his reflection being handsome. In "Brian Sings and Swings", he tells Lois, "Remember what I always tell you, if I come home in the middle of the day and catch you having sex with someone, I'll kill you both" (though when he catches her in bed with Bill Clinton in "Bill and Peter's Bogus Journey", he takes no hostile actions whatsoever). However, he seems not to mind the fact that she, of course, slept with other men before they met, just so long as she doesn't do so again; he is particularly proud of the fact that she once slept with Gene Simmons of Kiss when he discovers this in "Road to Europe", but forbids any sexual actions between the two now as seen in "Don't Make Me Over".
Peter seems to find it frustrating when he is "wrong" while Lois is "right" about issues all the time, and apparently takes these issues competitively, just waiting for the day she slips up. This day finally comes in the episode "PTV" after settling a conflict with Lois about censorship on television that she appeared sure to win. In an ironic twist that forces Lois to concede defeat, Peter celebrates by opening a secret compartment within the ceiling containing balloons, streamers, confetti, and a banner reading "PETER'S RIGHT!"; Peter then claims that he set up the stall 15 years ago, suggesting that this was a pretty major issue for him for quite some time (there was also a clown in the stall, but he had since died after being in there for so long). Curiously, in the non-canon episode "Da Boom", after Lois admits he was right about the end of the world and she was wrong, Peter makes no reference to the compartment, though he had been bragging about his "victory" for two weeks straight.
Among the members of his family, he tends to treat his daughter, Meg with the least amount of respect; in "Peter's Daughter", for example, he reminisces to various pranks he played on her, including tripping her, flicking her nose with his finger, and even shooting her at one point. He is known to embarrass her at times and with things that mean the most to Meg; the entire family once huddled together to read her diary and continues after Meg catches them. However, later episodes of the series show Peter developing greater respect and unity between himself and his daughter (such as in "Hell Comes to Quahog", "Road to Rupert" and the aforementioned "Peter's Daughter"), though these moments tend not to last for very long.
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