Kim Kardashian West‘s daughterNorth WestandKourtney Kardashian‘s daughterPenelope Disickmade a splash on the red carpet Tuesday, as they celebratedJoJo Siwa‘s sweet 16.

The cousins and BFFs — North, 5, and Penelope, 6½ — posed alongside Siwa and a few of their friends (including 6-year-old Ryan Romulus, the daughter ofKanye West‘s publicist Tracy Nguyen Romulus) at the birthday party, held at the W Hollywood in Los Angeles.

They looked happy could be, smiling wide for photographers. North wore a sparkling green top, pink shorts, and silver shoes — a colorful ensemble she highlighted with a rainbow fannypack and oversized hair bow. Penelope, meanwhile, wore a rainbow sequin tracksuit with a black T-shirt and rainbow boots.

At one point, the girls all flashed a big peace sign at the camera.

Ryan Romulus, North West, JoJo Siwa, Penelope Disick and guest at JoJo Siwa’s Sweet 16 Birthday celebration.Axelle/Bauer-Griffin/FilmMagic

JoJo Siwa Celebrates Her Sweet 16 Birthday

Paul Archuleta/FilmMagic

JoJo Siwa Celebrates Her Sweet 16 Birthday

Siwa, aDance Momsalum and YouTuber, has long been a favorite celeb of North’s.

Their afternoon together, which Kim helped set up, was filmed and posted on Siwa’s YouTube channel on March 31. The nearly 7-minute video begins with Kim, 38, dropping off her daughter before North and Siwa — in matching rainbow side ponytails — take a tour Siwa’s very colorful house.

North appeared to have had a ball. At one point, she showed off her splits during dance time toSiwa’s single “Bop”and climbed all over the singer’s infamous custom BMW (dubbed the Dreamer Mobile).

So what was North’s favorite part of the whole day? “Making a big mess,” she told her famous mom.

“Oh my God, you did make a big mess! Hey, you have to go clean up your mess,” Kim told North, who enthusiastically agreed that it was the best day of her life.

To top it all off, North was gifted with tickets toSiwa’sD.R.E.A.M. The Tourconcert— an event for which the singer encouraged North to bring Penelope.

JoJo Siwa/Instagram

north-west

“I had so much fun getting to film with North and@kimkardashian. Seriously North is SO adorable and awesome, and Kim is one of the SWEETEST people ever!” the teen sensation alsoshared on Instagram.

Siwa’s birthday event will be part of a Nickelodeon special entitledJoJo’s Dream Birthday, set to air on May 18 at 8 p.m.

source: people.com