- Not to be confused with Alonzo Hawk.
Alonzo is first seen when Cruella enters the House of DeVil at the start of the live-action film, busy trying to direct several phone calls coming in at once, and quite panicked as a result. However, he still stands up to greet Cruella.
When Cruella takes Anita to her office, she scolds Alonzo by reminding him to ask Anita if she wanted a drink. She then shouts at him when he hesitates to take the drawing from Anita and give it to her. Once he does, Cruella tells him to stand somewhere till she needs him. He is then ordered to give the drawing back to Anita when Cruella makes an addition to the design.
He is later seen at Cruella's home, when Horace and Jasper present the tiger skin coat to Cruella. His hands are shown to have a nervous shake as he pours them tea.
After Cruella is released from prison, reformed by Dr. Pavlov's therapy, Alonzo greets her with a gift - a Chinese crested dog whom she named Fluffy. As soon as Cruella arrives back at her house, he is given the job of burying all her furs in an underground chamber, including her design for the Dalmatian puppy coat. Subsequently, he helps her working with the dogs at Second Chance dog shelter.
When Cruella is reverted to normal, Alonzo, desperate to please her, is sent out to steal the puppies needed for her coat, while she meets with furrier Jean-Pierre Le Pelt. When he shows up with the captured puppies, Le Pelt takes an instant dislike to him, calling him a wormy little man. Alonzo also is landed with the job of looking after Fluffy, as Cruella is back to her dog-hating ways. Alonzo also reluctantly helps place evidence and Dalmatian puppies to frame Kevin Shepherd - the owner of the Second Chance dog shelter - for the crime, and then to steal the puppies back from under the police's noses. Upon arriving at the train station, which the Orient Express is taking Cruella, Le Pelt, and the captured Dalmatians to Paris, Alonzo is tasked with eliminating Oddball, as Cruella only wants spotted puppies for her coat. When Oddball manages to elude him, resulting in Alonzo getting his hands run over by a baggage trolley, he decides to let her go and return to the train, telling Cruella she will never see Oddball again.
After arriving in Paris, Alonzo's resentment of Le Pelt grows when the furrier gets to ride in Cruella's car while he has to follow in the van with the puppies. He is present when Cruella traps Kevin and Chloe Simon - Cruella's probation officer - in the basement of Le Pelt's sweatshop. Once inside, Alonzo is the first to notice the puppies escaping, although he tries to cover the fact. When Cruella notices, she yells at him for not killing Oddball, then storms off to recapture the puppies, causing Le Pelt to jeer at him again. Finally fed up, Alonzo engages Le Pelt in hand-to-hand combat, resulting in Le Pelt becoming trapped in the hole through which the puppies had escaped, and Chomp bites Le Pelt on the leg, causing him to scream, and Alonzo gags him by putting a fur tail scarf in his mouth. Alonzo then immediately frees Kevin and Chloe, telling them that the puppies are in the bakery nearby.
Later, Alonzo shows up at the Second Chance dog shelter with eight million pounds for the shelter - on the judge's orders, all of Cruella's money had gone to the dogs' homes of the borough of Westminster - of which "Second Chance" is the only one. While what happened to Alonzo subsequently is unconfirmed, it could be assumed that he started working at Second Chance as well.
Alonzo makes a small cameo on the second page of 101 Dalmatians: Animated Storybook. If the player clicks on a buzzer, Cruella shall press it and order Alonzo to get to where she is. When he arrives, Cruella asks what took him so long, and he apologizes for it. Cruella then tells him to stand somewhere till she needs him, and he walks off.
Whilst this is yet unconfirmed, in the series episode "Barnboozled", when Cruella moves into the barn, she demands to know where her cappuccino maker is, and a butler, having a similar resemblance to Alonzo, appears. He is later seen taking Cadpig's squeaky toy from her, when Cruella (annoyed by its noise) demands to have it.
- Alonzo did not appear in the original animated 1961 film nor its sequel. He was created specifically for the live-action version of this film and its sequel, 102 Dalmatians.
- In the credits of 102 Dalmatians, his name is spelled "Alonso".