The birthday girl's celebratory weekend started out simply enough, with a sushi lunch at Sugar Fish in Calabasas, California, on Saturday with sister Kendall Jenner, father Bruce Jenner, and several friends. The pals also honored the Keeping Up With the Kardashians star by wearing trucker hats with her face plastered upon them.
"Thank u to my friends for making this day so special so far. Happy birfday to me," she wrote.
That night, things got a little less innocent. Rocking a black dress with a slit-up-to-there, the teen queen danced on a table to 50 Cent's "In Da Club" while Kendall, Bieber, Brown, The Game, and rapper Tyga, along with a rather large, enthusiastic crowd cheered her on.
It seems that the Jenners' fellow underage star in attendance, Bieber, 20, was on his best behavior and seemed to stay out of trouble at the soiree. He sang "Happy Birthday" to Kylie, and posted a sweet, oddly paternal message to his "younger" friend.
"Happy birthday @kyliejenner ;) glad I got to spend it with u," he shared before adding, "So dope watching u grow up." Alongside the birthday wishes, Bieber posted a pretty Instagram shot of the budding reality star. In the pic (taken a few weeks ago, when the reality star had blue hair), the Rebels: City of Indra scribe stares at the camera with wide eyes and plucks at her pouty lips.
While we can't be sure what exactly went on at her bash, we do know she had a grand ol' time. Kylie posted a snapshot of her birthday cake, which was very big and very gold. "Thank u everyone & T for the cake & JB for singing happy bday to me. I love u guys," she captioned the photo.
But her birthday festivities didn't end there. On Sunday, which happens to be her actual date of birth, Kylie celebrated with Kendall and big sis Kim Kardashian at the Teen Choice Awards, where Keeping Up With the Kardashians earned top honors for Choice Reality Show.
Clad in a black crop top and a high-waisted gold-toned skirt, the brunette beauty looked every bit the lady as she took the stage with her sisters. "It's my birthday! This has been the most awesome birthday present ever so thank you!" Kylie gushed to the audience while accepting the iconic surfboard.Now the question is what she's going to do to top all this next year when she turns 18… and Bieber is 21.