Selena Gomez and Charlize Theron unite for WE Day celebrations

Selena Gomez, Demi Lovato, and Charlize Theron were among the stars who gathered on Thursday (07Apr16) to celebrate the annual WE Day festivities.

The celebrities made special guest appearances at the first WE Day bash ever to take place in California, using their star power to deliver inspirational speeches in a bid to encourage youths to continue making a difference in their local and global communities through charitable efforts.

Selena kicked off the proceedings at the Forum in Inglewood, where 16,000 local students sang and danced along to her performance of hit single Kill Em With Kindness.

"Today is my fourth time on the We Day stage," Selena told the crowd before her set. "I continue to be inspired by the young people who are breaking down barriers and creating real change around the world."

She also took to Instagram to share a photo of herself backstage, writing, "@weday I am proud to be apart of what you do to inspire the world. WE are the next generation. By grace through faith."

Meanwhile, Charlize, who served as the honorary co-chair of WE Day California, urged young fans to become the generation that ends the AIDS problem, while Seth Rogen and his wife Lauren, whose mother suffers from Alzheimer's disease, discussed how their own family struggles had inspired them to start a charity to raise money for dementia research, reports The Associated Press.

Zooey Deschanel and the cast of her hit comedy New Girl also called on kids to spread love and encouraged the students to take part in a big group hug.

Joe Jonas, rapper Big Sean, Darren Criss, Modern Family actor Rico Rodriguez, Room star Jacob Tremblay, and married couple Nikki Reed and Ian Somerhalder also featured at the event, while Demi hit the stage to belt out her song Stone Cold as part of the day's musical entertainment.

Other guests in attendance included Henry Winkler, Martin Sheen, Amandla Stenberg, Paula Abdul, Tyrese Gibson and Kermit the Frog.