Mason Disick had a birthday party straight out of a movie [1] on Saturday. Kourtney Kardashian and Scott Disick's son, who turns 5 in December, was surrounded by his mom's famous sisters, including Khloé Kardashian and Kendall and Kylie Jenner, at an early celebration in LA. Complete with Christmas trees covered in spiderwebs, the picture-perfect party captured the mood of Tim Burton's The Nightmare Before Christmas. In a series of Instagram snaps, the group showed off the festive decorations and face makeup, courtesy of artist Joyce Bonelli.

It's been about six months since reports of Kourtney's third child with Scott emerged. The reality star's pregnancy physique was front and center when she slipped into a bikini for some fun in the sun [2] in September. The following month, she revealed her growing baby bump while treating her children, Mason and Penelope, to a day at the pumpkin patch [3]. Meanwhile, Kourtney's sister Kendall also has a lot to celebrate — on Saturday, Estée Lauder announced that Kendall is the new face [4] of its brand with a short video about her transformation. Keep reading to see pictures of the family celebrating Mason's birthday!

Kendall shared a collage of pictures taken at the party.

In the caption for her picture with Kylie, Khloé pointed out that "Kourtney pulled a 'mean girl' move on me and had me dress like Sally from The Nightmare Before Christmas while everyone else was mad chill."

Kourtney captured the spooky Christmas-meets-Halloween party decorations.

Pal Joyce Bonelli held her son, Zeplin Black, in this shot with Khloé and Kendall.

Kendall and Khloé showed off their makeup in a selfie.