Apple TV+'s Severance star Marc Geller, who plays the enigmatic Kier Eagan, has spilled some behind-the-scenes secrets from the gripping season two finale, Cold Harbor.

The episode saw a pivotal moment with Mr Milchick, portrayed by Tramell Tillman, interacting with an oversized animatronic version of Kier, reports the Irish Star.

In an exclusive chat with the Irish Star, Geller divulged details about the sequence featuring Milchick and the bizarre animatronic figure.

As the face and voice behind Kier in Severance, Geller is featured in every image, sculpture, and recording throughout the show, including those in the Perpetuity Wing and Woe's Hollow.

Geller shared his on-set experience: "I was actually on set for the filming for the animatronic. Usually, I'm in a studio with [director] Ben [Stiller] and a technician recording, but for timing reasons I was there all that week and I got to do with Tramell."

He added, "I could watch Tramell and the mannequin on the monitor for timing and see what they were doing. That was great. It was great to be there with the other actors and to be able to interact with people."

Expanding on the impact of this interaction, he said: "It gives it a whole new feeling. You're actually talking to other people, there are people to relate to and they're giving something back which changes your performance.

"If I'm doing it in the studio, I'm not getting anything back from anyone, so Tramell's reactions influenced how I would say the next line."

Geller also revealed an interesting tidbit about Milchick's jab at the animatronic, noting that it stood five inches taller than the actual Kier.

Geller shared details about an amusing incident on set, "What happened was, we did the reading one day. That line was not in there. And then Ben loves to take pictures and he wanted to take some pictures of me next to the mannequin."

He added, revealing the size contrast, "And the mannequin is really very tall, like 6ft 2in and I'm like 5ft 7in. So I was nowhere near the head level of the mannequin."

During a particularly humorous photo shoot, Geller recounted his efforts to match up to the mannequin's height as Stiller worked the animatronic, "I was trying so hard to get up to that level and I turned to Tramell and I said, 'Why is this mannequin five inches taller than me?' And then the next day when I came in to shoot, that was the line in the script," Geller unveiled.

He bagged the role of Kier in March 2020 just before the Covid pandemic struck, putting the globe on pause.

Initially, Geller was brought on board simply to mimic Kier's appearance, resulting in an extensive Benjamin Button-like photo session that went on for 10 hours.

Explaining the transformation from hirsute to well-groomed through the course of a day, Geller noted that he began with a hearty beard and untamed, lengthy hair due to lockdown, only to emerge fresh-faced with short, dark hair, mirroring Kier's reverse aging process.

Geller holds a double duty as the Lumon founder; he isn't just the face behind Kier but lends his voice to the character as well.

Fans were under the mistaken impression that Ben Stiller was playing Kier - in reality, although the Zoolander actor did a brief cameo for Helly's congratulatory video in Severance season one, it has been Kier all along.

The Severance star is now making waves, his most prominent role to date, with an acting history including A Different Man alongside Sebastian Stan, Katy Keene, and Russian Doll.

Hailing from Rhode Island, Geller has had aspirations of becoming an actor since his childhood days, staging plays and roping in others for his early productions.

Without any family ties to the showbiz world, this didn't halt Geller's ambition.

In a push towards his dreams, he persuaded his parents to enrol him in a children's theatre school in neighbouring Massachusetts after spotting an advert in the newspaper.

Geller cut his teeth on stage, starting in community and local theatre, before taking the plunge to New York at 18 to chase a professional acting career.

Moving into film and television auditions in 2018, Geller found he "really enjoyed a lot" and decided it would be his "primary focus".

His resume continues to grow, with IMDb noting his next appearance in the anticipated Marvel series 'Daredevil: Born Again'.

The hit series 'Severance' has undoubtedly amplified Geller's fame, with the actor enjoying his increased recognition, humorously commenting: "I never shy away from a 'Praise Kier'."

Severance seasons 1 & 2 are streaming on Apple TV+ now