Saoirse Ronan's horse in 'Mary Queen of Scots' was "the biggest diva".
The 24-year-old star learnt to ride an equine for the first time with Prince - the same stallion as DC Comics superhero Wonder Woman - for the drama and she has described her noble steed as being both "really cocky" and "nervous".
She told W magazine: "I got to learn how to ride a horse for Mary 'Queen of Scots'.
"My horse is also Wonder Woman's horse, and he is the biggest diva I've ever met in my life. "His name's Prince. And Prince doesn't do anything for anyone, especially me.
"So, I'd be on the horse and I'd be like, 'Come on, Prince. Let's go!'
"And I'm trying to be all sort of Queen-like and he'd just look at me and he'd go, 'I'm not ready to go yet.' And then he'd go from being like really, really cocky to getting really nervous."
She quipped: "Yeah. Everything I did was for that horse, just to get his approval."
The 'Lady Bird' star recently revealed she found it "awkward" going to the toilet in a corset whilst filming the movie, which sees her star as the titular Mary Stuart alongside her on-screen rival, Margot Robbie's Queen Elizabeth I.
Ronan admitted it was rather "uncomfortable" being in the garment, which synchs the waist in, especially when she needed to use the bathroom.
She said: "They weren't uncomfortable, just difficult to wear. We had to navigate our way around the corsets and five skirts we wore every day, and I had to ride horses in them. It was a whole new thing, so I got used to it."
Asked if it was difficult using the lavatory, she replied: "Yes, but I'm not going to go into that."
Despite her struggles wearing the tight-fitted clothing, Saoirse said it was an "amazing feeling" when she was working on the film because the project was a dream come true.
She said: "The film focuses on the seven years before Mary's arrest in England and we see Queen Elizabeth heavily involved in the politics of that time and the struggle against patriarchal authority.
"I've always wanted to play Mary and it was an amazing feeling to get to do it."