It showed Leslie, who played Snow's love interest Ygritte on GoT, opening the fridge in their United Kingdom home and noticing something inside, before screaming and collapsing on the floor.
"My family does April Fools", Kit told Jonathan, "Her family doesn't do April Fools".
In the clip, an unsuspecting Leslie approaches their fridge to retrieve a Brita filter to find that Harington replaced the milk with a decapitated replica of his head. "I did have some plans to do it; I was going to string up some lights in some trees and do all the romantic stuff", explains Harington.
While the two's romance has been pretty strong, Harington also recounts how Leslie threatened him that their relationship would be over if he ever made a prank as bad as that again.
Harington adds that much like the proposal, the wedding will definitely notbe Game of Thrones-themed (sorry, superfans). I mean, can you blame her?
The couple, who met on the Game of Thrones set while filming in Iceland, announced their engagement last month.
It looks like Jon Snow knows SOMETHING!
Leslie had been mostly silent about their romance, only revealing to The Telegraph previous year that keeping it secret while they were on set together was a challenge.