Everyone knows dressing as 'yourself' just doesn't cut it at fancy dress parties.
And nor does coming as Jon Snow - if you're Kit Harington, at least.
According to Heat magazine, Harington's fiancée Rose Leslie experienced an odd turn of inspiration before a fancy dress party.
She pulled out a Jon Snow costume and whispered in Harington's ear:
I won't love you if you don't wear it.
Harington promptly did what he was told, rocking up to the party very in-character.
But what theme could inspire Leslie to choose a costume that had brought her future husband unimaginable success, a frenzy of fans and critical acclaim?
No, not Game of Thrones or even 'fantasy characters' - but 'bad taste'.
Even worse, the costume wasn't even from Harington's dressing room, but a fancy dress shop.
Yes, he had to deal with slightly ill-fitting, lame-looking get-up for once. Just like the rest of us.
Harington said to Heat magazine:
It was really embarrassing.
The people bringing around canapes were looking at me, thinking 'You're a sad man! You've come to a party dressed as your character.'
Harington definitely deserved it though, after pranking Leslie with a severed head in the fridge.