Mischa Barton is on the cover of Cosmopolitan's April 2019 issue with Whitney Port, Audrina Patridge, and Heidi Pratt.

The four stars are part of the cast for the upcoming "Hills" reboot that will premiere on MTV in the summer, titled "The Hills: New Beginnings."

People are confused as to why Barton is included in the cast, since she wasn't part of the original reality TV series.

The actress actually rose to fame thanks to her role on "The O.C.," which inspired "Laguna Beach" and led to "The Hills."

Mischa Barton is joining "The Hills'" reboot, and fans are seriously confused.

"The Hills: New Beginnings" is scheduled to hit MTV this summer and the cast includes original "Hills" members Whitney Port, Audrina Patridge, Heidi Pratt, Spencer Pratt, Stephanie Pratt, Brody Jenner, Frankie Delgado, Jason Wahler, and Justin "Bobby" Brescia.

"The Hills," which premiered on MTV in 2006 and lasted for six seasons, followed the success of "Laguna Beach: The Real Orange County." One of the new additions to "The Hills: New Beginnings" is Mischa Barton. The actress became well-known in the early 2000s when she starred as Marissa Cooper on the scripted drama "The O.C.," which served as inspiration for "Laguna Beach."

After Cosmopolitan released an April 2019 cover story that featured Port, Patridge, Heidi Pratt, and Barton, fans took to Twitter to react to the "O.C." star joining the cast. Many were confused since Barton wasn't part of the original "Hills."

Others are wondering how the reboot will work, considering that Conrad, one of the most prominent "Hills" stars, won't be participating.

Read more: 21 surprising things you never knew about 'The Hills'

Conrad isn't the only "Hills" member who's missing from the reboot. Kristin Cavallari also won't be part of the show.

"They're not part of the story line," Port told Cosmopolitan.

Barton, who revealed that she joined the show in October 2018, also explained that despite not being on the original reality TV series, she ran in similar circles.

"It's weird because I remember going out with Nicole Richie and people at the time, and we would come by set when they were filming 'The Hills,'" she told Cosmopolitan. "She would drag me to the producer van to see what you guys had been up to all day. All these years later ... it sounds corny, but it felt like this was supposed to happen."

The 33-year-old added that she "was approached by a million different people for a long period of time" before finally signing on for "The Hills: New Beginnings."