Salma Hayek fangirls over 'The Eternals' co-star Kit Harington in Instagram photo

Salma Hayek may be one of the world’s biggest Hollywood stars but even she is prone to fangirling.

Kit Harington - who recently came out of a stint in rehab after self-referring himself to work on some "personal issues" - was the target of her appreciation in a photo she posted of the two of them on Instagram.

Hayek is a massive Game of Thrones fans and captioned the snap: "I still can't believe that I'm working with #jonsnow ! Kit you're the best."

The two are working together on the upcoming Marvel movie The Eternals which boasts an impressive cast.

Hayek plays leader of the Eternal Ajak, a character who has been gender-swapped for the movie, while Harington was announced in the cast at Disney’s D23 Expo, as non-Eternal Dane Whitman.

Whitman also goes by the name Black Knight and has a relationship with Gemma Chan’s Eternal character Sersei

Read more: All the Marvel news from D23 Expo

Barry Keoghan, of The Killing of a Sacred Deer fame, joined the previously announced cast at D23 Expo to confirm his role as a new Eternal called Druig.

Richard Madden (Ikaris), Kumail Nanjiani (Kingo), Angelina Jolie (Thena), Salma Hayek (Ajak), Lauren Ridloff (Makkari, Brian Tyree Henry (Phastos), Lia McHugh (Sprite) and Don Lee (Gilgamesh) were all in attendance to reveal their costumes for the Marvel movie about gods fighting gods, directed by Chloe Zhao.

Read more: Every Marvel movie and TV show on the release schedule

This mystical Marvel movie is set millions of years before the events of the Infinity Saga “when the cosmic beings known as the Celestials genetically experimented on humans, creating the super-powered individuals” called The Eternals as well as the more villainous group The Deviants.

As the film’s synopsis says: “the two groups went on to battle each other throughout history to see which would eventually become the ultimate race.

“The story involves the love story between Ikaris, a man fueled by cosmic energy, and Sersi, who relishes in moving amongst humans.”

MCU fans will be aware of the Celestials thanks to the Guardians of the Galaxy franchise; Knowhere, the home of the Collector, is actually the head of a dead Celestial while Peter Quill’s dear dad Ego is one of them too.

Then there’s Thanos, who is a Titan Eternal himself, while the Kree and Skrull races (seen in Captain Marvel) have their own history with certain Eternals too.

Filming began in August in Atlanta and the movie is set for release on November 6, 2020.