Interesting fact:

In a show of shocking moments and twists, perhaps The Red Wedding takes the cake for most memorable of them all. Some of the actors and crew were kept totally unaware of what was to transpire. Even Rory McCann, who plays The Hound, did not know the details of what was happening inside the hall until he watched the episode. Richard Madden, who plays Robb Stark, is also said to have learnt of his character’s fate through internet forums.