켄달 제너 그리고 헤일리 비버 let their hair down on Sunday for 빌리 아일리시‘s 21st birthday party.

The supermodels were slightly misbehaving with tongues out and middle fingers blazing in black-and-white photo booth snaps at the Christmas-themed bash. On Jenner’s Instagram Stories, she showcased solo shots of the three pals and a couple silly pics sporting various sneers while Bieber gave a kissy face.

Eilish was dressed as Mrs. Claus in a sexy Santa suit. She had a three-tier cake decked out with peppermint candies for the milestone affair, which was lined with disco balls hanging from the ceiling.

Per videos shared on Eilish’s own Instagram Stories, guests raised their glass for the “나쁜 사람” singer in a birthday toast. Her boyfriend, Jesse Rutherford, and Hailey’s husband, 저스틴 비버, 도 참석했다, 와 함께 도자 고양이, 에이브릴 라빈 그리고 Noah Cyrus.

제너, 27, appeared to be flying solo for the night. Several sources confirmed to PEOPLE last month that the 카다시안 star and Phoenix Suns guard Devin Booker “quietly” ended their relationship in October due to their demanding jobs.

“Both have incredibly busy schedules right now with their careers and they’ve decided to make that a priority,” 소식통은 사람들에게 말합니다.. For Jenner, 27, that includes her 818 tequila line and her booming modeling career, and for Booker, 26, it’s his involvement with the NBA.

“They have a lot of love and respect for each other and wish only the best,” another source added.

As for Hailey, 26, she and her longtime love appear to be going strong, constantly supporting one another on social media. 저스틴, 28, announced in June that he has a facial paralysis condition called Ramsay Hunt syndrome and Hailey suffered from a mini-stroke 3월에.

While doing press for her new skincare line, the YSL model opened up about her scary episode and Justin’s recent diagnosis.

스토리를 놓치지 마세요. PEOPLE의 무료 일간 뉴스레터 PEOPLE이 제공하는 최고의 최신 정보를 유지하기 위해, 흥미진진한 유명인 뉴스부터 흥미진진한 스토리까지.

“We both are dealing with older illnesses for sure,” she joked on 켈리와 라이언과 함께 살기, before getting reflective. “Honestly the silver lining in the whole situation — what he went through, what I went through — is it really bonds you. I feel like we’re closer than ever. It really brings us close. So I’ll take that away from it.”

She echoed the sentiment on 굿모닝 아메리카, adding that having to go through health scares publicly pushed the couple closer — and to be open with one another about everything. “It in a way forces you to have to just be upfront about what’s going on so that people understand what you’re going through,” Hailey said. “I actually think it opened up a lot of really important and amazing conversation.”