George R.R Martin has admitted that he wanted to see Lady Stoneheart appear in the show as she has a major role in the books. Speaking at Medill School of Journalism, where he received an alumni award for his achievements, GRRM was asked which characters from the books he’d like to see on Game of Thrones.
“Lady Stoneheart. It was a major storyline in the books. (Also) Arianne Martell. Her character wasn’t included.”
** Spoiler Alert **
In case you don’t know, Lady Stoneheart is the resurrected version of Catelyn Stark, after she and her son Robb were brutally murdered at the Red Wedding. She was brought back to life by Lord Beric Dondarrion, who gave his life for hers. Her exclusion from the show has received a huge backlash, especially from the book readers, and the showrunners have maintained that she will not appear in Game of Thrones.