Lindsay Lohan Joins 'Mean Girls' Co-Stars to Celebrate October 3 - Find out How!

It’s October 3 – otherwise known as Mean Girls Day!

15 years after the theatrical release of the movie, Lindsay Lohan and her Mean Girls co-stars teamed up for an amazing cause on the fan-created holiday, which honors a line in the movie.

PHOTOS: Check out the latest pics of Lindsay Lohan

Amanda Seyfried, Lizzy Caplan, Lacey Chabert, Jonathan Bennett, Rajiv Surendra, Daniel Franzese, Jan Caruana and Stephanie Drummond all teamed up for a group video.

The cast is raising money for The Thirst Project, which aims to provide safe drinking water to all people in the country by 2022.

Watch their announcement inside…