Before you dispute me on my choice, it's Lore time:
"The Miraculous were created in a time when man and wild lived together. When harnessing the power of the Kwamis, they deemed that a bearer would assume a human form if they weren't of man already. This was to preserve secrecy of who had the jewels and the power themselves. Animals were considered suitable since humans already tended to underestimate their kind already.
However, a nasty vie for power in what would be known as the Cold Lair resulted in a schism between humans and the wild for generation to come. A new policy was decreed: the Miraculous could not be trusted with humans lest the world falls to ruin.
Shere Khan's theft of the Butterfly Miraculous and eventually Akuma attacks meant that the Ladybug was needed but not without powerful support. Akela knew the situation was desperate to let Plagg choose his new bearer amongst the Seeonee Wolf Pack. Suffice to say, the power of destruction would go to somebody that would make the mystics themselves roll in their graves.
As Akela's granddaughter, Lala grew up to be a bitch in every sense of the human's derogatory term. She was often quick with a cutting remark and to take out her bad mood on others. Lala could also be a bit of diva when it came to holding her head up a touch too high. For older pack members, they knew that she was only going through what they saw as a tomboy phase with the lack of a mother figure. For younger members... no, she was pain full stop.
Especially towards Mowgli the man-cub. She'd often cut into his hunts if they crossed paths and show him up, especially to rub in how he'd never be a real wolf. The man-cub would hardly take it up the tailbone but rarely got the last word in. Lala was the most vocal to object to him joining the pack and even challenged him to hunt more prey than her to present to Akela if she wanted his vote.
Her grandfather agreed to this if only to propose that the younger members perform a hunting excersise as a way to prepare for Shere Khan. In truth, this was a cover for the Kwamis to scout their promising new bearers. Plagg found himself drawn to Lala when it came to her attitude and related to how she didn't care about how others saw her. His hand was forced when Tabaqui was akumatized by Shere Khan, now Hawk Moth, and turned into a rock beast.
Stone Heart interrupted Lala's hunt and chased her through the woods. Quick thinking and dodging bought her time to hide before Plagg revealed himself. Lala recognized the Miraculous as that of her father's, Vermillion, and felt her bravado get its second wind. Plagg was about to explain it all when she snatched the ring and slipped it onto her wrist, the camouflage charm allowing it to seem like any other accessory.
"Plagg, Claws Out!" Lala shouted. Plagg protested but was soon drawn into the Miraculous and transformed the wolf into a half-human half cat heroine. She even struck a pose upon revealing herself to Stone Heart as if she'd rehearsed for this very moment.
Chat Noire, as she declared herself, had trouble using her extendable staff and found herself on the run again. She was saved by her agility spiking but soon found herself on a cliff. Mowgli bailed her out with his boomerang and even caught her in his arms much to her embarassment. However, Stone Heart soon came crashing down. By instinct, Chat Noire grabbed Mowgli and extended her staff to vault him to safety.
Knowing better now, she returned to the fray but only could've won with the help of the new Ladybug swooping in to her side. Though Lala's haughtiness showed, she played herself off as more playful and charming like the heroes she heard of. It helped that Ladybug's ingenuity earned her admiration when they purified the Akuma. She even felt a rare sense of guilt when Tabaqui admitted that Lala's sharp tongue made him vulnerable to Akumatization.
Before splitting up, the two heroez gave a fist bump to commemorate their first outting. However, they had to keep their identities mum to each other lest Hawk Moth got a hold of one and squealed on the other. They took their time bantering about while slinging and vaulting through the Jungle for practice. If they only knew that their new best friends had been their worst enemies...
The challenge ended with both Mowgli and Lala finding both their prey collection to have been snatched by scavengers. With the pair of them both losing, Lala scoffed and ate crow by giving her vote for Mowgli to stay. She even told the man-cub that she'll be sure to not let him outdo her. Sharing a cocky grin with her new rivals, something changed in Lala. Small but noticeable.
And thus, the most unlikely pair became the only things keeping Shere Khan at bay..."
In Jungle Book: Shonen Mowgli, Lala is based on Leela, a minor character from Rudyard Kipling's novel, and expanded on in an minor on again, off again role as Mowgli's, well, mean girl. The Chloe Bourgeois to Mowgli's Marinette. So... why here as Chat Noir...e?
Well... it homages the original plan for Felix to be the Cat bearer rather than Adrien with him being standoffish towards Marinette. Here it's more like Lala sees a need to prove herself against Mowgli and vice versa. As Chat Noire, Lala is a lot more likable towards Ladybug both as a means to work together and to show the hidden depth beneath the priss she parades herself as.
It would play into the overall themes of identity and belonging, especially when new enemies enter the fray.
