The Prince of Winterfell - S2-E8
Continuity mistake: In the scene where Tyrion and Cersei are talking about sending Joffrey to the battlefield, Tyrion removes his cloth napkin from his shirt twice. (01:18:50)
The Ghost of Harrenhal - S2-E5
Continuity mistake: Brienne and Lady Catelyn are with their horses by a stream talking. Brienne's white horse is walked into picture and is very dirty. The next shot the horse is clean. (00:38:40)
The Old Gods and the New - S2-E6
Continuity mistake: When Maester Luwin walks towards Theon to try and talk him out of executing Ser Rodrik, he places his right hand on Theon's left shoulder. When the shot changes, his hand is no longer on Theon's shoulder.
Continuity mistake: When Tyrion is explaining where he has been and what he has been doing, he grabs a jug of wine by the neck. When the camera changes he now has it by the body of the jug. (00:07:30)
Chosen answer: Well Magic does come to mind. The White Walkers bring with them the winter. Because of this, the seasons are very unpredictable. "Winter Is Coming" refers to this.
lionhead