The Kardashian Preschoolers Had a Mermaid-Themed Birthday Party, and We're Actually a Little Envious

It was an all-out, under-the-sea extravaganza for North West and Penelope Disick on Saturday. The cousins celebrated their birthdays together at a mermaid-themed party attended by nearly the whole Kardashian-Jenner brood—and they gave us a glimpse of all the festivities via social media (not that we expected anything less).

For those having hard time keeping up with the family's many birthdays, North turned three on Wednesday, and Penelope will be four on July 8. The two attended their birthday bash wearing adorable matching mermaid costumes.

Even Penelope's older brother Mason got in on the celebration.

The party was held outdoors, complete with plenty of balloons, on what looks to have been a gorgeous Southern California day. Both Kim Kardashian-West and Kylie Jenner captured the ocean-themed decor on Snapchat.

On Snapchat, aunts Khloe and Kylie filmed the girls on the kitchen counter, happily flapping their mermaid tails next to their own individual mermaid cakes and blowing out their candles as guests serenaded them with "Happy Birthday."

And Kylie captured Kim Kardashian-West's outfit of the day: a white top and green mermaid tail, complete with long pearl necklace.

ICYMI, Khloé donned a lavender wig for the occasion, per the birthday girls' request. "When your nieces request you wear lavender hair to their mermaid party. You wear lavender hair. Anything for my babies!" she wrote on Instagram.

Khloe also posted Snapchat videos with Kylie, acknowledging that her younger sister is usually the one wearing the wigs, and with Scott Disick, where she jokes that today she's "Becky with the pink hair."

By the looks of it, this birthday party was one that those two little mermaids won't soon forget.

Are you a Kardashian expert? Put your knowledge to the test in the video below: