'KUTWK': Kendall Jenner Gets Down and Dirty Confronting Sister Kourtney Over 'Bullying' Claims

Things got heated between Kendall Jenner and Kourtney Kardashian during Sunday's episode of Keeping Up With the Kardashians. The sisters were forced to navigate some serious tension after a trip to Mammoth Mountain in California went sour.

Early in the episode Jenner, 23, revealed that she let Kardashian tag along with her and her friends on the trip. She shared with sister Khloe Kardashian that the trip didn't go exactly how she planned, admitting that she felt the Poosh founder had been "a bit rude."

Jenner accused her big sister of "trying to be cool," making several jokes at her expense. Her friends didn't join in on ribbing her — at least not to her face — but all laughed along at Kourtney's seemingly mean-spirited jokes.

The model told Khloe that the drama began in the car on the way to Mammoth, when Kourtney put her "muddy" shoes all over the car and told her to "chill the f--- out" when she asked a friend to be careful not to lose her keys while skiing.

Kourtney recalled the drama very differently, telling Khloe that Kendall was high-strung throughout the entire vacation. She recalled a particular incident that allegedly occurred while grocery shopping, at which time Kendall insisted that no one go off the grocery list. Kourtney claimed Kendall made a big deal of a friend wanting potatoes, which weren't on her list, so she offered to cover them.

She went on to accuse Kendall of being "so f---ing annoying," but admitted she did tease her a bit. Still, Kourtney said it was "unfair" of Kendall to call her a bully.

"I definitely think it was unfair for Kendall to say I was bullying her," she said. "We were just having a good time. She's just way more uptight and I thought, because I wasn't trying to make fun of her at all."

Khloe relayed that information to Kendall, who called Kourtney to discuss the potato incident. She claimed it never happened, and Kourtney was quick to dismiss her.

"Listen, I don't have time to talk with a lunatic. We can talk when you're ready to talk like an adult," she said before hanging up.

After speaking with both her sisters about the drama, Khloe decided to act. She popped by Kourtney's for a visit, and invited Kendall over to talk things out. The visit quickly turned explosive, with both sisters yelling at each other — and Khloe — and no resolution reached.

"It seems like you are saying or doing things to bring yourself up at my expense, like to make yourself seem funnier, or cooler," Jenner said to Kourtney, who claimed she "didn't even know there was a problem."

"Why are you telling the story back and forth to everybody?" Kourtney shouted at Khloe. "Are you in 3rd grade?"

Both Jenner and Kourtney walked away from the confrontation more annoyed than when it began. The mother-of-three admitted in a confessional interview it was "really annoying" knowing that Khloe had gone back to their little sister with information she shared with her "in confidence."

Just when Khloe thought things couldn't get any tenser between the pair, she walked out on Kourtney's lawn to find her and Jenner wrestling. When the scrap was over, the sisters revealed that they were only playing around, and had actually planned the fight to get back at Khloe for meddling in their drama.

"We came to the conclusion that Khloe made this a little bit worse than it needed to be," Jenner said in a confessional. "So, we decided to stage a little fight to annoy Khloe and freak her out a bit for getting into our business."

Khloe was adamant that she was merely trying to help, but confessed that she may have gone about the wrong way.

"I thought I was doing a good thing," she said. "I was sincerely trying to help, but I know for the next time just let them figure it out on their own."

Keeping Up With the Kardashians airs Sundays at 9 p.m. ET on E!