The Three Diablos are three orphaned kittens who served as henchmen for a French thief known as the Whisperer.
They aided the Whisperer in stealing the Heart of Fire Ruby but were captured in the process while their master escaped. Puss in Boots is hired to get the ruby back and takes custody of the kittens to coax them into leading him to the Whisperer's hideout.
Puss, fooled by the Diablos' apparent cuteness and innocence, makes the mistake of underestimating them, and they chain him up with their manacles so they can get the key from him to free themselves. Afterwards they proceed to playfully torture Puss in several painful and demeaning ways, and end it by literally burying Puss alive.
As they start finding their way back to the Whisperer, they are confronted by Puss, who managed to dig himself free, and enter a hissing standoff before it becomes a battle between the innocent kitten look between Puss and the Diablos. They almost win but in the end are overwhelmed by Puss's innocent kitten eyes.
Puss ties them up and as nightfalls, he states they should be ashamed and consider what their mama would think. But seeing their faces, he realizes they have no mama and are orphans. Puss reveals he too is an orphan, and how a friend of his led him down the wrong path the same way the Whisperer has led the Diablos. He then avows to point them in the right direction and cuts them free of their bindings. He names the female Diablo Perla, for being one of a kind, the tortoiseshell tabby kitten Gonzalo, for his scrappy temper, and he hesitates with the last kitten before naming him Sir Timoteo Montenegro III "because sometimes a title is all you need".
Puss then proceeds to train them and play with them, becoming close to them, until finally he tells them a bedtime story until they fall asleep.
In the morning, the Diablos lead them to the Whisperer's hideout, and the thief promptly reveals himself, prompting the Diablos to hide in fear. Realizing the Diablos had betrayed him, the Whisperer proceeds to threaten them, only for Puss to raise his sword in their defense and tells them to run. The Whisperer manages to corner Puss but the Diablos save him with the same fighting techniques Puss trained them with, ending with the recovery of the ruby, and the Whisperer accidentally falling to his death.
In the end, Puss returns the ruby to the princess and is rewarded, at which point he presents the princess with the Diablos as her new personal guards, which is met with mixed results but still accepted. Puss then gives each Diablo a gold coin but Timmy swallows his, thinking his brother and sister were eating theirs. The Diablos say goodbye to Puss and he leaves.
At first, the Three Diablos seem like cute and innocent kittens, but looks can be deceiving. They make full use of their cuteness to lower their victims' guard and promptly jump `em, subdue them, and playfully torture them.
Perla - The only girl among them, appears to be the leader, and keeps a close watch on her brothers, and while she's very devious (being the one who came up with the idea to bury Puss alive), she's really a sweet little one, and is the one with creamy gold and white fur and in red pinkish boots.
Gonzalo - Is the tortoiseshell but was named for his scrappy temper, and the most brutal, shown when he tortured Puss the most out of his siblings, and threw sand into Puss's eyes. He's very brave and often the first to show it, with pride and bravado.
Sir Timoteo Montenegro III - Or Timmy for short, is the gray and white chubby kitten but is rather slow, not very bright, and easily distracted. Even so, he's as capable of deviousness and torture as his brother and sister, though he's often smacked on the head to get his attention or led by his sister. Otherwise, he just follows his brother and sister's lead.
Truthfully, the Diablos are just three little kittens who were led down the wrong path, but were pointed by Puss in the right direction. And they are truly playful kittens at heart, seen when they played with Puss after he convinced them to be better than what they originally were, and like any kids, they love a good bedtime story.
The Diablos formed a loving bond with Puss, who became the closest thing they ever had to a real parent.
The Three Diablos are three crafty, sneaky, devious, and somewhat sadistic kittens. They are skilled in maintaining the facade of three cute and innocent kittens to easily lower their victims' guard, making it all the easier to jump `em, subdue them, and torture them.
Their methods of torture are both playful and demeaning but nevertheless painful. Like Puss in Boots, they are capable of using a cute, wide-eyed expression to soften their foes' hearts, though they do it together for more effectiveness. They almost overwhelmed Puss this way (of course they cheated with Gonzalo throwing sand in Puss' eyes) but in the end Puss' cute stare dazed and overwhelmed them.
After becoming friends with Puss, he trained them to fight like him, and use his techniques, including his trademark aerial cartwheel jump, and possibly in swordsmanship, as they were each given wooden swords.