The 30-year-old actor had left it too late to shop for a costume for a 'bad taste' bash and when a sales assistant, who didn't recognise him, suggested it would be funny for him to capitalise on his likeness and dress as Jon Snow, his fiancee Rose Leslie was delighted with the idea and made him wear the outfit, much to his later embarrassment.
He said: "I was in Aberdeen and I left it really late to get a costume.
"So I went to the one costume shop that was open in Aberdeen and the woman who worked there said, 'You know, you really look like the guy from 'Game of Thrones' and I've got a 'Game of Thrones' outfit.'
"She pulled out a Jon Snow costume and Rose just whispered in my ear, 'I won't love you if you don't [wear it]... You should do it.'
"I went to the bad taste party dressed as Jon Snow. Which was really embarrassing.
"The people bringing round canapes were looking at me, thinking, 'You saaaaaad man. You've come to a party dressed as your character.'
"I think the woman in the shop realised who I was as I was leaving.
"But that's even sadder - me going to a fancy dress shop and buying a Jon Snow costume."
Kit also had to don period costume for his role in TV drama 'Gunpowder' and he claimed he now has a "problem" where modern dress in other roles, such as when he played a former MI5 agent in 2015 spy film 'Spooks: The Greater Good', makes it harder to get into character.
He told heat magazine: "I may actually have a problem, which is that when I put on jeans for a role, I don't feel like I'm playing a character.
"I've been doing roles for so long where I'm in cloaks and very specific types of leathers.
"So when I put on my Jon Snow outfit, I suddenly feel like, 'Yes, I am a character'. The weight of the costume helps too...
"It's so different when I do a modern role, like when I did the 'Spooks' film - I was basically wearing what I would normally wear and I found it really hard to find that character."