With production underway on The Walking Dead spinoff Fear the Walking Dead, new cast members are slowly but surely being added to the newish apocalyptic world.

Actresses Mercedes Mason and Elizabeth Rodriguez have been cast in mystery roles, and the former is being described as a series regular. Both ladies were cast after the pilot was shot earlier this year, so don’t expect either character to be appearing in Fear the Walking Dead’s premiere episode.

Rodriguez is best known for her role as inmate Aleida Diaz, Dayanara’s mother, in Netflix’s Orange is the New Black, which is set to premiere its third season this June. Mason has had roles in a slew of television programs, including NCIS: Los Angeles and 666 Park Avenue.

If The Walking Dead is any indication, there’s a high chance there will be many characters in Fear who come and go frequently from the core group. It’s only natural that the group will be ever evolving — especially at the start of a crazy outbreak like this one.

Fear the Walking Dead is set in Los Angeles and focuses on the same zombie outbreak seen in The Walking Dead, but Fear will follow a completely different set of characters and begin its story before the outbreak occurs.

Cliff Curtis, Kim Dickens, Frank Dilate, and Alycia Debnam Carey have the lead roles — until they’re all killed off and replaced by others, that is.

The new series will premiere late this summer before The Walking Dead season 6 launches. AMC has already renewed the show for a second season, airing in 2016.

And yes, Fear the Walking Dead is the show’s real title.