I came up with this as a possible reason as to why Kiara has a personality change from how she was in Simba's Pride to how she is in The Lion Guard, along with a "How Kion met Bunga" headcanon. I might turn this into something more grand-scale once the series gets underfoot, trying to tie it in with Simba's Pride.

No More Fun

"I can't believe the one time I get sick, you run off to the Outlands."

Kiara knew her brother couldn't see her with their backs facing each other, but that didn't stop her from directing an annoyed glare in the direction of his hushed voice. The cubs had turned in earlier than the rest of the pride that night, what with Kion feeling under the weather and with Kiara being temporarily punished for her earlier escapade.

"Wasn't like I planned it," Kiara defended herself in a whisper. The only others in the den were Timon and Pumbaa, who had passed out from exhaustion, but she still didn't want to chance anyone overhearing her. "And like you would've followed me out there."

"I might've."

Kiara rolled her eyes, having heard the uncertainty laced in his words. "Whatever. It's done now. Future Queen Kiara the Rebellious Troublemaker strikes again," she stated flatly.

Kion rolled onto his back, his paws tucked up to his chest, as he glanced at his sister curiously. "Why so glum?"

"Why do you think?"

"'Cause you got in trouble? That's nothing new, for either of us actually."

Kiara sighed, her eyes gazing out past the den's entrance which showcased the last light of day. The stars would show themselves soon. "I met another cub today."

"Huh?"

"In the Outlands," she continued, her legs curling up against her. "There was a cub out there, a boy."

Kion yawned before turning his head to let out a tiny sneeze. Kiara would kill him if he'd sneezed on her. "Guess he was breaking his parents' rules about visiting that place. Odd coincidence."

"No. He said he lived there. Even called himself an Outsider."

"What?" Kion accidentally squeaked the word a bit too loud. He cringed, his ears flattening, as the sleeping Timon changed positions from his sleeping spot on tomp of Pumbaa. "That's crazy, only hyenas live out there," he whispered once he figured it was safe to talk again.

"You didn't see him, Kion." She flipped over so they could talk face-to-face. "He was scrawny, and so was his mother." Kiara shuddered lightly, hoping to herself that she never had to encounter that vicious lioness again. "He didn't even know how to play. He was so serious. It was weird. And when his mother took him away, they went further into the Outlands. I think they have a whole pride out there."

Kion rolled over onto his side, frowning at his sister's tone and expression. He wasn't accustomed to seeing Kiara being so somber. "I wonder why no one's ever told us about other lions before? Did Dad say anything when he showed up to get you?"

"He definitely knew that lioness. She was saying crazy stuff about how our lands belong to Scar." She mimicked Zira's nasty words in a sarcastic manner, rolling her eyes. "It was kinda scary. Kovu, that was the cub's name, looked pretty scared too, so I don't know if he knew anything either."

"That's...pretty crazy, sis," Kion said gently, his ears folded back. "I'm sorry I wasn't there. And I'm glad you're okay."

"Yeah..." Kiara sighed again. "I just felt like I got dropped in the middle of some bigger story without being prepared. Like, what if I had known all the history of the Pridelands beforehand? What if I actually took being Future Queen seriously?"

Kion snorted lightly which only made his nose itch. He suppressed a sneeze for his sister's sake. "Are you serious? You hate all the princess stuff."

"I know, but it's still my destiny. I can't exactly change our birthing order."

"That's good, because I definitely don't want to be Future King. But c'mon, Kiara, lighten up a little."

Kiara shut her eyes, looking deep in thought. "No. I can't. I started so much trouble today. I don't even know the full extent of it, but it was all because I was bored and got curious about the Outlands." Her eyes began to well up with tears. "If I had just followed the rules and acted like I was supposed to, nothing bad would've happened."

Kion didn't know what to say. He had never seen Kiara cry before, and he felt frustrated that he couldn't think of anything helpful to say. Kiara wiped at her face with a paw, turning herself around to where her back would be facing Kion.

"Good night," she said, thus ending any more potential conversation.

"Yeah," Kion said back, glancing at her worriedly before he rested his head down. Maybe she'd be better in the morning, back to her usual self.

The sun rose twice in the sky before Kion was back in top form, eager to take on the world again. He bounded out of the den, squinting at his old friend the sun for a few moments before racing down the side of Pride Rock. Kiara had not been there when he'd woken up, so he was off to find her. She had been quiet ever since she told him about her adventure in the Outlands, and he was still pretty worried about her.

He finally spotted her, talking with two other female cubs that were in the pride, Zuri and Tiifu. Kion thought that was a little weird, as Kiara didn't really have much in common with them. They thought all the adventuring that the royal siblings did was too messy and dangerous. He didn't think too much about it, assuming that she was just so bored that she was willing to spend time with them. Or maybe she was trying to be a good princess and be friendly.

"There you are!" Kion said loudly as he approached the trio. "Hey, sis, wanna go mess with those monkeys that live near the river? I bet we can dare them to do some more crazy stunts! Or play hide-and-seek or chase crickets or-"

"Sorry, Kion," Zuri cleared her throat in disapproval. "Kiara isn't interested in doing those childish things anymore."

"What?" Kion looked over at Kiara, who had her tail swirled around her legs in a sheepish manner and was avoiding eye contact. "That's ridiculous!"

"She was just telling us that she wants to be more prim and proper, like a true princess should be," Zuri continued as she observed her freshly shined claws. "You could probably take a few tips from her."

"Kiara, what is she blabbing about?" Kion wanted to know, looking rather hurt. "You don't want to play with me anymore?"

His sister set her jaw, straightening herself up to make herself look a little taller, her chest puffed out. "If I'm going to be Queen one day, I need to start acting the part. I don't want to be an adult and not have any clue what I'm doing, do I? I have to get my life together. If you were smart, little brother, you'd be doing the same thing."

Kion could hardly believe his ears, his mouth agape. "You...you're serious? You were actually serious, what you said the other ni-"

"Now if you'll excuse me, I have other things to attend to," Kiara interrupted him, turning her back on him with a flick of her tail. "Let's go, ladies."

Tiifu stayed silent, looking at Kion in an apologetic manner before dashing off after the princess. Zuri stuck her nose in her air, carefully trotting along after them. Kion sat down hard on his haunches, feeling dejected. He suddenly felt more alone than he ever had in his life. Kion finally forced himself to stand, slowly walking back from whence he came, his head hanging down as a couple of tears rolled down his nose.

Gone was his sister, replaced by a snooty clone.

He wasn't granted much more time to mope before something hard bounced off his skull. Kion yelped in pain, falling backwards as he rubbed his head with his front paws. "What in the-"

"Oops, sorry about that, friend!" He heard a chipper voice call out. The voice soon had a face attached to it, that of a young honey badger. Kion had heard about these creatures from the hunting party when they returned with their kills, often speaking of their great ferocity. The young prince scooted back a little in case this was a hostile encounter, making the newcomer tilt his head in confusion. "Hey, what gives? No need to be scared of me! I'm not gonna hurt you on purpose! Name's Bunga, what's yours?"

Kion looked bewildered at this friendly show, but he did relax considerably. "Um...Kion." Maybe only adult honey badgers were mean. Or maybe the hunting party just liked embellishing their tales for the sake of theatrics.

"No way!" Bunga gasped, his eyes huge. "I mean, you're King Simba's son, right? Zuka zama, that's so awesome! Hey, you want to play baobab ball with me? That's what hit you in the head earlier," the honey badger known as Bunga explained, scooping up fruit in his claws. "Whattaya say? It's not much fun playing by myself."

Kion looked back in the direction that he had left Kiara in, sighing a bit. It would take time to get over the pain of losing his sister as a friend, but perhaps having fun with a new friend would help cure it faster. "Sure, why not?" Kion said with a small smile.

Kiara sighed as she looked down from the large rock that she was stretched out on. The girls had taken to napping in the sun, Tiifu's ears twitching when a bug got too close. The princess yawned, not from being tired but rather from being bored. She looked down when she heard the familiar sound of her brother laughing, looking surprised when she saw him playing with what looked like a young honey badger. Her ears fell, wishing she could join in.

No, she told herself. She had to take her destiny seriously now, or bad things would happen. What if something were to happen to Kion, or their parents, because she was too busy goofing off instead of learning to be a proper Lion Queen?

Her mind was made up. The time for fun and child's play was over.