Cobblepot, better known as the Penguin, is the only character from Batman's rogue's gallery to have significant screen time, but he is also further from the source material than the rest of the characters. Edward Nygma (the Riddler) has a few cryptic lines as the coroner, Ivy Pepper (Poison Ivy) is simply the daughter of a suspect, and Selina Kyle (Catwoman) is a teenage pickpocket watching from the sidelines. None of them make an impact on the story and are just introduced for future reference (although Ivy might be motivated in the future by this episode's events), but Cobblepot is a major plot-driving character and splashes on screen.
Surprisingly, Cobblepot is also significantly different from the many interpretations of the character. He's a lackey to crime boss Mooney, relegated to rubbing her feet and holding her umbrella, rather than an established criminal mastermind. While he desires power and attempts to usurp Mooney, he differs from the Penguin we know, and his childlike glee at hurting a fellow criminal is creepy and unsettling. The disheveled character we get in Gotham is distinct from his source material and proves to be a much more interesting character for it.
His boss, Fish Mooney is the only original character in the episode and provides a primary antagonist for the pilot. Smith is fantastic at making Mooney sweet, sinister, or calculating, but her best trick is maintaining Mooney's powerful rage behind these facades. The end result is a controlling character that is fantastic at manipulating others while Smith communicates that fury to the audience, making her kind of terrifying.
Most of the problems of Gotham City and its police are communicated through Harvey Bullock. Bullock is in danger of falling into tropes, thanks to his pessimistic worldview, bottle of antacid, and heavy drinking. Luckily, Logue saves the character, adding enough expression to make him enjoyable to see on screen and, whether intentional or not, to make his motives questionable. He demands that Gordon either compromise his values or get out of the way, but there's enough hints to know that Bullock was forced into this position, too.
In the climax, Bullock tells Gordon to execute Cobblepot on behalf of Gotham's head crime boss, Carmine Falcone. Gordon fakes the execution and Bullock's "Good boy" is nuanced enough to leave it open to interpretation. While it seems that Bullock believes Gordon killed Cobblepot, Bullock is no moron and it may be that he is glad that Gordon has found a way to play the game.