James Gunn has teased a mystery star will appear in 'Guardians of the Galaxy Vol. 3'.

The 55-year-old director confirmed on Friday (06.05.22) night that filming for the final installment of the series has wrapped as he explained Zoe Saldana was missing from his behind-the-scenes photo because the only one he has with her in also included her mystery co-star.

Sharing a photo of himself laughing with Chris Pratt, Pom Klementieff, Karen Gillan, Dave Bautista and his brother Sean Gunn, he wrote: "And that's a picture wrap on the Guardians of the Galaxy trilogy.

"I love this amazing cast crew their beautiful talent kind souls. I'm a lucky human to have them on the journey with me for nearly a decade.

"And yes Zoe was with us but the only picture I have with her has an unannounced actor with us!"

James previously admitted there had been a "lot of sadness" on the set of the film - which is due for release in May 2023 - because everyone was aware it was their last outing.

A Twitter user asked: “Mr Gunn, how are the vibes on set?”

In reply, James tweeted: “Honestly they’re great, I love this cast and crew, but there is also a lot of sadness and near-daily tears knowing this is the last Guardians movie for most of us. #gotgvol3.”

The filmmaker previously admitted it was "a little bit scary" to be ending the saga.

He said: "I just want to be true to the characters, the story and give people the wrap-up that they deserve for the story... That’s always a little bit scary; I'm doing my best."

The 'Suicide Squad' director also promised the flick with be “big” and “different” from what people might think it will be.

He said: "It's big; it’s so, so big and dark, and different from what people might be expecting it to be."