Despite being a petty criminal, Fagin is essentially a good man driven to desperate measures to repay a debt to Bill Sykes. He greatly appreciates the attention of his dogs, and understandably sees them as his own children. He is portrayed as somewhat illiterate, and he is absolutely terrified of Sykes - this is not cowardice, for he is indeed a terrifying man.
At the end, he shows himself to be brave and not without a sense of honor and morality, playing a strong part in saving Jenny Foxworth from Sykes. He is kind, cowardly, friendly, gentle, nice, generous, good-hearted, shrewd, and clumsy.
Fagin is first seen entering his barge with dog biscuits in hand while yelling at his dogs, telling them to stop their game "fight", which grabs their attention. They then leap onto him and welcome him home, licking his face despite his protests. Just as he is enjoying himself, Sykes, to whom he has been lent a considerable sum of money, arrives. He looks at the "loot" the dogs have brought in and is dismayed to find it is all broken rubbish. He even notices Oliver.
Then, Sykes' Dobermans, Roscoe and DeSoto arrive, before Fagin can examine Oliver, and shoo him away so as to talk to their master. Having little choice, Fagin heads up to offer the items to Sykes anyway, who tells him that he doesn't want his garbage, but his money. He begs for more time. Possibly because he knows dead men can't pay money back, Sykes gives him three more days, then honks his horn to call his dogs back, which frightens Fagin; causing him to fall off the dock and into the bay. He returns, drenched, to the barge; lamenting that he simply can't pay off all that money in just three days. His dogs comfort him (mostly Einstein) by giving him a dog biscuit to eat and then licking him after he thanks them. Then, he says he saw DeSoto's nose and asks who did it. Dodger picks up and reveals Oliver to him, meaning he's the one who did it, and Fagin comments that they could use all the help they can get and is proud that it was him. When it's time for bed, Einstein insists Fagin reads them a bedtime story. At first, he is reluctant because he's too tired, but when he hears and sees Einstein whining sadly, he accepts "but just 1 chapter" and later, they go to sleep.
The next day, Fagin drives with Oliver and the gang into the city on his scooter, leaves Dodger responsible for everything concerning Oliver, and informs the dogs that "Dead men do not buy dog food." therefore, telling them to "get out there and fetch". He then attempts to pawn his broken wares while the dogs and Oliver go on the hunt for money, merchandise, and food after agreeing with Dodger about helping Fagin with his financial problems with Sykes.
At the end of the second day, Oliver, who now has a new home and owner from yesterday, was "saved" by the dogs, and is sad because he wanted to stay, is returned to the barge, where Fagin notices his new collar and the wealthy district it is addressed to, after taking him back in when he was intending to leave to go back to his new owner. He has the idea to ransom Oliver and, after dropping off the ransom note and rendezvous map to Oliver's owner, Jenny Foxworth (unknown to him), goes with Dodger to see Sykes with his offer after going over his plan about the ransom, pretending Dodger is Sykes. At first, Sykes, seeing Fagin doesn't have the cash in hand and hearing him discussing his plan with him awkwardly at first, sets Roscoe and DeSoto on him with one snap of his fingers, and Dodger protects him while he gabbles out his desperate plan loudly and properly this time and shows him Oliver as proof. After Sykes is convinced, he snaps his fingers again to tell his dogs to cease the attack. Then, he notices Jenny's address engraved on Oliver's collar and assumes that Fagin is planning to kidnap her and gives him 12 more hours as his "last chance" when feeding dog biscuits to his dogs while Fagin and Oliver come to Dodger's aid after he lays injured and unconscious and having received severe (but invisible) injuries from the attack.
On the same night, Fagin meets Jenny and her pet poodle, Georgette. Not realizing at first that she is Oliver's wealthy owner, he advises her to go home, given the tough neighborhood she's in. When she tells him that she's lost, he then asks her what she's doing at the shipyards by herself in the first place. He is visibly shocked when she tells him that she came to get her stolen cat back and has brought nothing more than a piggy bank as payment. Fagin tries defending the "kidnapper" saying he is a "poor desperate man" but Jenny breaks down into tears anyway. Feeling guilty, he finally follows his good heart by giving up and pretending to find Oliver in a box, giving him back to her. Sykes, who was watching the whole thing with his dogs in his car, makes his move, snatching Jenny, tossing Oliver out the window, and telling a shocked Fagin to keep his mouth shut and to consider their account closed.
Then, Dodger and the gang come to Oliver's aid. He assures him that they'll "absitively" get Jenny back. They run to Sykes' warehouse without riding in Fagin's scooter this time. After they rescue Jenny, Fagin saves them from Sykes in the scooter. Thinking Sykes will not follow him in his car, he heads into a subway station and onto the tracks. Sykes follows him anyway and, during the climatic chase, Jenny is thrown onto the hood of Sykes' car, after it collides with the scooter. Fagin leaves the driving to the dogs (specifically Tito) and tries to reach for Jenny when she calls for his help, with Einstein holding him, while Dodger and Oliver are fighting off Roscoe and DeSoto. Eventually, she makes a jump, after having been caught by Sykes on the leg and then released, thanks to Oliver and Dodger, and he catches her as Tito drives the gang (except Oliver and Dodger) in the scooter onto one of the Brooklyn Bridge's suspension cables when a train is spotted heading their way; escaping the same death as Sykes by inches. When the rest of the company drive back down, Jenny runs to search for Oliver, only to find a sad Dodger approaching; holding a "thought to be dead" Oliver. At first, everyone thinks he is dead too but when Jenny hears him making a soft mew, she quickly realizes that he is alive and everyone is rejoiced, except Georgette, who is still in great shock from the chase. Then, Dodger and the rest of the gang are accepted as Jenny's new best friends.
The next day, at Jenny's home, during her eighth birthday party, Fagin encounters Winston, the Foxworths' butler, sings "Happy Birthday" with him to Jenny, and apparently makes a bet with him on the outcome of a wrestling game. When his fighter loses and he can't pay up, he sidles out of the house by using the time to leave as an excuse while grabbing an apple on his way before driving off with the dogs. Then, he says his good-byes to Jenny. Outside the mansion, after Fagin starts up his scooter, Winston gets smudged by its smoke. At the end, free from his debt by Sykes and with him and his dogs dead, Fagin is free to start a new, more honest life, or at the very least, his previous life of petty crime; free from the threat of a painful death. He is last seen driving, with the gang singing "Why Should I Worry" reprise, in his scooter as Jenny, Winston, and Oliver say good-bye to them and watch them as they return home.
Fagin appears in House of Genius along with Kaa, Ronno, Governor Ratcliffe, Bongo, one of the 99 dalmatian puppies, Johnny Appleseed, Cinderella, Ratigan, Prince Charming, Sonia, a Rhino, Pecos Bill, Colonel, and Tigger while waiting at the entrance for a seat.
In Goofy's Menu Magic, he appeared with the same characters (except for Cinderella, Prince Charming, the Rhino, Pecos Bill, and Tigger replaced by Genie, a Centaurette, Tito, Pinocchio, Baloo, and Rachel instead) waiting to get their next "magic" meal from Goofy.
- It is never explained how a poor man such as Fagin came to be in possession of valuable purebreds like his dog friends, although it is possible that he either stole them or found them as strays and took them under his wing at some point.
- In one of the earliest stages of production, the artists came up with four possible places for Fagin and his dogs to live in. The first was an old abandoned subway station, the second was a condemned building near the docks, which in the past had been a very famous theatre, the third was in the sewers beneath the Plaza Hotel, and the fourth was his boathouse, which ended up being chosen for story purposes.
- Fagin wears four (presumably stolen) watches on his left arm. One of them has a picture of Mickey Mouse on it.
- Although it is stated in the film that Fagin owes money to Sykes, it is never said what the exact amount was or when Fagin borrowed the money.
- Dom DeLuise, Fagin's voice actor, was actually famous for voicing several characters from Don Bluth's movies until his death such as Jeremy in The Secret of NIMH, Tiger in An American Tail, Itchy in All Dogs Go to Heaven, and Stanley in A Troll in Central Park. He already had roles in several other animated films by this point, but this was the only time he got the chance to voice a character in a Disney film. He loved the role so much, he kept ad-libbing lines that ended up being included in the film.
- In the original script, there was a flashback scene which explained that Fagin ended up owing money to Sykes, after borrowing it to participate in an illegal poker tournament in Chinatown, where he lost everything.
- The man Fagin tries to pawn his watch to is a caricature of Peter Schneider, then vice-president of Disney animation.
- During the chase, where Jenny is hanging on the front of Sykes' car, she yells Fagin's name for help. Slightly later, Fagin yells for Jennifer to jump. The two never introduced themselves earlier in the film, yet know each other's names.
- During the chase on the bridge, Fagin's scooter jumps from the railway tracks to the bridge support wires. After it makes the jump, there's a medium shot of Dodger and Oliver attacking Sykes. In this shot, the scooter can be briefly seen on the left of the screen riding on the bridge supports. The previously full scooter is now completely empty (with not even a driver).
- Fagin may have a gambling problem, as seen with his bet with Winston, despite not having any money. This would explain why he needed money from Sykes in the first place, to pay off his debts.