Kendall & Kylie Jenner Unlock Inner Fangirls During Backstreet Boys Performance in Balmain X H&M After Party [Photos]

Kendall Jenner along with her sister Kylie Jenner, best pal Gigi Hadid and the rest of the models of Balmain x H&M fashion show brought out their inner fangirls when the Backstreet Boys came out with a surprise performance. The 90s group stunned everyone as they set to close the runway with their greatest hits.

According to Mashable, the American vocal group suddenly emerged for the show finale and sang their iconic songs "Everybody [Backstreet's Back]" followed by "I Want It That Way." Band member Brian Litrell went down of the stage and headed to the 19-year-old "KUWTK' favorite and serenaded her with a few lines which she crooned along.

Too, the girlfriend of Joe Jonas and Alessandra Ambrosio were spotted singing with the crowd. Backstreet Boys also showcased their signature dance moves and it seemed like nothing has changed -- from 1999 until now. Kendall together with her BFF Gigi, her 18-year-old youngest sibling and Balmain designer Olivier Rousteing were all standing on the front row to have the full view of the boy band's production. Hollywood Life reported that the television personality was evidently having the time of her life as she danced and mouthing every single word of Backstreet Boy's lyrics. Us Weekly also noted that the A-lister audience made their way across the runway to the balconies to watch the group's performance. They also slayed their millennium hit "Larger Than Life" which people danced along.

However, before everyone went wild on the appearance of Backstreet Boys, there was a solemn fashion show. Elle wrote that the Balmain and H&M collaboration featured the favorite and famous catwalkers of today.

Kendall led all the models by opening the runway while Gigi did her signature catwalk to close the show. Bella Hadid, Karlie Kloss and Joan Smalls, too, graced the platform to showcase their beautiful body, wearing the unique ensembles.

Moreover, the runway was differently designed with several stretches and a flight of long stairs. The designers left the traditional one long straight catwalk and made their models strutted three flights while wearing their sky-high heels.

Meanwhile, Kylie was present on the event to support her sister while, Rosie Huntington-Whiteley, Diane Kruger , Martha Hunt, Ellie Goulding, Alek Wek, Zachary Quinto and Alexa Chung were all there to witness the show.

French Montana, Khloe Kardashian's former lover, was also spotted on the bash as cited by Hollywood Life. The 30-year-old rapper managed to talk and took pictures with the Jenner sisters to show there's no bad blood between him and the famous family.