Every Game of Thronesfan remembers how Robb and Catelyn died in the TV show (as well as in A Song of Ice and Fire book series). It's really hard to forget the Red Wedding. According to George R.R. Martin's 1993 letter to Harper Collins, however, Robb and Catelyn's storylines were supposed to be very different.
Robb Stark's death.
According to the letter, after Ned Stark is executed Cate and Arya return to Winterfell while the war inflames throughout the north. Robb Stark is the one who leads the Northern soldiers into battle. After several, brilliant victories against the Lannisters army, Robb fights Joffrey Baratheon on the battlefield and mutilates the young "Baratheon".
As reported in the letter, in the end Robb is "not able to stand against Jaime, Tyrion and their allies" and he is killed on the battlefield, while Joffrey will survive despite the injuries.
Catelyn escaping Winterfell.
As reported in the letter, after Robb's defeat Tyrion Lannister besieges and then burn Winterfell, forcing Catelyn, Bran and Arya to move north (apparently, there is no Rickon in Martin's original plan for A Game of Thrones). Hoping to be protected by Benjen Stark and Jon Snow, Ned's wife arrives at the Wall, but the Night Watch's men can't help her because of their oath, and Cate makes what it looks like a very bad decision: she goes even further north.
Catelyn Tully's death.
Beyond the Wall, Cate, Bran and Arya are captured by Mance Rayder.
Shortly after, Cate and her children encounter the White Walkers. The Others attack the wildling camp and, despite "Bran's magic", "Arya's sword Needle" and the ferocity of their direwolves, Catelyn is killed by the Others.
Brandon and Arya will survive the fight and, later in the books, they will find a valuable ally in Tyrion Lannister, who will join the Starks after his brother Jaime took the Iron Throne killing off any other pretenders and blaming the murders on Tyrion. We suggest you to read our previous article on George R.R. Martin's original plan for A Song of Ice and Fire if you want to know who Jon and Tyrion were supposed to be in love with!