Papi is a male Chihuaha who belongs to Sam the landscaper. One day, Papi notices Chloe lounging by the pool, and he immediately develops a crush on her. He woos her with a grasshopper and calls her "Mi Corazone," but she rejects the gift and Papi as well. Later, when Papi finds out that Chloe was dog-napped, he sets out to find her because he's in love with her and deeply cares for her.
Chloe gets caught by Vasquez (thanks to the GPS he had placed on El Diablo's collar, which he used to track her) and is locked in a cage. Fortunately, Papi arrives and helps Chloe escape, although he gets captured as well. When Chloe frees him, Diablo corners Papi while Vasquez tries to catch Chloe. When Chloe discovers her inner bark and scares Vasquez away, she then attacks Diablo, although he throws her aside, knocking her unconscious.
After Diablo is defeated by Delgado, Papi discovers Chloe passed out and assumes she is dead. With tears in his eyes, Papi begins soothing her with beautiful words that explain how much he loves her. Chloe wakes up and tells him not to stop. Papi is relieved that she is okay and even happier that Chole finally accepts his love for her. Sam and Rachel find the two dogs and take them home.
Back in Beverly Hills, Papi and Chloe relax on the patio. Chloe thanks Papi for his help and tells him that she loves him in Spanish, and she licks him down to the ground as her way of showing her love. Before the end credits, Papi explains what happens to the dogs (Chloe's friends that she met in Mexico) and Chloe's Beverly Hills friends, and he and Chloe have five puppies.
Papi reappears in the second film with his wife Chloe. They have five puppies named Papi Jr., Lala, Rosa, Ali and Pep, which they try to keep up with. Papi tells his kids some incredible tales about the heroic Chihuahua. However, he embellishes his stories to the point in which the puppies end up causing mayhem. Chloe believes that Papi is too easygoing and suggests he starts showing their kids a little discipline. Papi is reluctant to do so at first, but he eventually comes around in the end. Later, Papi and Chloe, along with Delgado and Pedro (Papi's adoptive brother), participate in a dog fashion show to win a large cash prize that would save Sam and Rachel's family house. Though Papi had initially won, because of the lack of breed papers, he is automatically disqualified. As a result, the dogs lose to an arrogant French poodle named Appoline, much to their chagrin.
Eager to help out with Delgado's deep situation concerning his sons: Alberto and Antonio (whom he had abandoned as puppies at a police station for protection), Papi and Chloe's kids venture out and eventually find some bank robbers who had stolen a large sum of money. The puppies stow away in one of the bags, but are later found out by the robbers. Papi and Chloe soon discover their kids missing, and they, along with Pedro and Delgado, set out to look for them. The dogs eventually locate the puppies and defeat the bank robbers. Papi scolds the kids for running off, but Chloe tells Papi that they did manage to capture the robbers and were trying to save their family home, so Papi lets the kids off lightly. The dogs return home to find that they have been awarded more than enough money to save Sam's family house. Papi and the dogs, along with their human owners, celebrate their victory and Sam and Rachel's engagement and live happily ever after.
Papi appears in the third film, where he is seen being a teacher to the puppies. When everybody moves in to the hotel, Papi learns there's a school for little dogs and that Rosa keeps feeling left out. He meets Jenny and Oscar. At the garden, he was seen working with Sam Cortez. However shortly, he began to grow suspicious on why Oscar kept going to the gate behind the garden. Pedro meets up with him, asking him for help to ask out Charlotte.
Papi decides to give Rosa a fiesta to celebrate her sweet 15 (in dog years). He and Sebastian were seen auditioning different dog bands. Later, Papi was seen in a mudbath after trying to spy on Oscar and Chole. When that failed, Papi heads back to the gate and then finds out what Jenny was really up to; to do stuff for the rival hotel to get money from Mr. Montague. He knew about her scheme, stating, "No one is that perky." Papi sneaks into the manager's office to see what Jenny was doing. Papi gets caught due to his tailwagging and was sent back to Sam.
That night, he hears a cry for help from the public pool from Charlotte (thinking it was Rosa). But when he was running with the other dogs, they accidently vandalized the garden. After Rosa saved Charlotte, he scolds Rosa for being at the big pool at night, alone, and without "swimmies." After hearing the heroic truth from Charlotte, Papi and the others decided to continue on with the fiesta, by reconstructing the garden.
The next day, Papi and Pedro used a rope to make Jenny trip and fall in the puddle of peanut butter. The hotel manager appears and after giving him evidence, he's said to have misjudged Papi and finds out the truth about Jenny. After Sam and Rachel Cortez got their jobs back, everyone was celebrating Rosa's fiesta. In the end, Papi was seen celebrating with everyone else.
- "Don't you usually pay for a mud mask? This one's free."
- "Don't look now, but I think someone shaved your heiny."
- "Ah, Papi likes. Papi likes."
- He is the only character whose voice actor reprises his voice for the whole trilogy.