Bristol's involvement has ruffled feathers among co-stars, as one source tells E! News the cast is "surprised and shocked" that producers cast someone outside the Teen Mom family.
"Cast members were under the impression from social media that Mackenzie McKee would be joining Teen Mom OG," the insider shares. "The OG's have largely been kept in the dark about casting, [and] now they're confused whether they're getting two new cast members or if producers are moving forward solely with Bristol."
Of course, Palin is no stranger to the ups and downs of reality television. She previously appeared on Dancing With the Stars, where she finished in third place, and starred in the Lifetime show Bristol Palin: Life's a Tripp. She'd go on to compete on an all-star season of Dancing With the Stars in 2012.
In a recent Instagram post, Bristol reflected on her first pregnancy: "10 years ago this week—my life took the biggest possible turn. I was 17 and a junior in high school... It took hearing your heartbeat for a positive pregnancy test to really mean anything to me, and took holding you in my arms to realize my life was going to be changed forever."
The Ashley's Reality TV Roundup reports that Bristol is already filming.
Previously confirmed cast members include Catelynn Lowell, Maci Bookout and Amber Portwood. It's also reported that The Challenge star Cheyenne Floyd is also set to join Teen Mom OG.
E! News has reached out to Bristol's rep and MTV for comment.
TMZ was first to break the story.