The pop star celebrated an early 36th birthday at a massive surprise party Saturday night and the 19-year-old Keeping Up With the Kardashians star and her BFFs were among the guests.
Kylie dressed up like Christina did at her performance of "Dirrty" on her MTV's TRL Presents: Christina Aguilera Stripped in NYC 2002 special, wearing a long, platinum blonde and black wig, a black and yellow striped string bikini and matching arm bands, plus chaps that read "XTINA."
Why? Because Christina asked her to!
Kylie had channeled the singer's similar look from her "Dirrty" music video on Halloween and Christina gave her seal of approval on Instagram.
Well, it turns out she liked the tribute so much that this time, she asked Kylie to dress up like her for her birthday.
"When XTINA wants u to dress as XTINA for her bday you do it !!!" the teen wrote on Snapchat.
And Kylie received her endorsement in person; At the bash, Christina, sporting flashy party sunglasses, a multi-colored fur coat and a large pink, curly wig similar to one she wore on The Voice, and the reality star cuddled up for a kiss.
"Happy Birthday @xtina !!!!!!" she wrote on Instagram, alongside a video of the two.
The party was held at Christina's house and lasted until about 1:30 a.m.
The bash had "Chaps and Tutus" theme and many sweet treats were served. Candy stations were placed around the room and the party also contained a piñata.
Christina received a three-tier cake with pastel pink, yellow and purple icing, decorated with doughnuts, multi-colored swirled lollipops, gumdrops and an upside down ice cream cone for a topper.
Also, keeping up with the holiday spirit, red Christmas trees adorned the room.
Christina was joined at the party by her fiancé, Matthew Rutler.
Other guests included Melissa McCarthy, who had a blast on the dance floor, The Voice alum and Curly Sue star Alisan Porter and singer and Real Housewives of Beverly Hills star Erika Jayne, who performed on the dance floor and also cuddled up to Christina, on a lavish loveseat.
The birthday girl had by that point ditched the coat, but kept the wig, and sported a black and leopard-print dress.
Christina had teased the party on Instagram with a photo of her wearing a fake candy-decorated sheer glove and her large wig resting beneath a glass of wine and a red lollypop.
"Get ready to party kiddies!" she wrote.