Mary-Kate And Ashley Olsen Celebrate Birthday With Olympic-Themed Bash

Let the games begin!

Mary-Kate and Ashley Olsen celebrated their 29th birthday with an Olympic-themed bash on Saturday in the Hamptons. The twin fashion designers invited their closest friends to enjoy the outdoor party that included dunk tanks, fireworks and obstacle courses.

Instead of cake, they served up a yummy ice cream bar including waffle bowls and sprinkles. The sisters also had their guests wear either "Team Mary-Kate" or "Team Ashley" t-shirts for the competition and everyone tagged their social media photos with #OlsenOlympics.