If you saw the last episode of 24: Live Another Day you saw something reminiscent of a certain scene in Game of Thrones. Entertainment Weekly has an interview with Michelle Fairley where she discusses both shows. Spoilers ahead.
Like Catelyn Stark, Fairley's character in 24, Margot Al-Harazi, watches her son being killed just before her own death. It's not the Red Wedding but I wasn't expecting Jack to throw her out the window either.
As for Catelyn Stark and Lady Stoneheart:
There was a lot of online conversation. I heard third-hand that you were basically told that it's not likely to ever happen. Is that accurate? Yeah, the character's dead. She's dead.
Do you have a preference at all—do you think Catelyn's arc should end where it ended, or would you be into the resurrection idea?
You respect the writers' decision. I knew the arc, and that was it. They can't stick to the books 100 percent. It's impossible—they only have 10 hours per season. They have got to keep it dramatic and exciting, and extraneous stuff along the way gets lost in order to maintain the quality of brilliant show.
Which is still vague enough to not really preclude the appearance of Lady Stoneheart.
You can read the interview here.