Celeste O'Connor and Logan Kim have joined 'Ghostbusters 2020'.

The original Ghostbusters

The original Ghostbusters

The newcomers are set to star in unknown roles in the forthcoming instalment of the comedy horror franchise alongside Paul Rudd, who will play a teacher in the film.

Announcing the casting, director Jason Reitman - whose father Ivan directed the original 1984 movie - said: "Celeste and Logan are rare talents and we're all grateful that they'll be lending their unique voices to 'GB20'."

'The Leftovers' star Carrie Coon, 'Stranger Things' actor Finn Wolfhard and 'Gifted' star Mckenna Grace will also have roles in the movie.

Reitman has co-written the screenplay with Gil Kenan, and plans are in place to start shooting the movie later this summer.

Reitman previously said of Rudd's casting: "I've been wanting to work with Paul Rudd since my short film opened for 'Wet Hot American Summer' at Sundance. I'm thrilled he'll be joining this new chapter in the original 'Ghostbusters' universe."

Although plot details are being kept under wraps, the story is believed to be an extension of the original movie, focusing on a single mother and her family.

It's not known how it will connect to the 1984 classic and 1989 sequel, but many stars from those films will reprise their roles.

Sigourney Weaver has revealed she will be back as cellist Dana Barrett, whose apartment was haunted by a demonic spirit in the first film.

She said: "It's going to be crazy working with the guys again!"

Speaking about the original 'Ghostbusters', she added: "I knew it would be big. The script was so funny and full of heart. 'Ghostbusters' changed my life."

Dan Aykroyd previously revealed the third instalment of the franchise is "so different" from the first two films, and feels the movie is more "warm" and "heartfelt" than its predecessors.

He explained: "It's so different from even the first and second (film)... This just takes it to a new generation and a new direction that is so warm, heartfelt and indeed, quite scary when you confront some of the issues that are being discussed."

Aykroyd starred as Dr. Ray Stantz alongside Bill Murray as Dr. Peter Venkman, the late Harold Ramis as Dr. Egon Spengler and Ernie Hudson as Winston Zeddemore, who comprised the original spook fighting squad.