Game of Thrones show-runners Dan Weiss and David Benioff have been pretty forthright in the past when it comes to the original pilot for their smash-hit HBO show. The consensus? It was not good. The full video has never been released to the public, though vestigial clues—like Theon’s and Tyrion’s mysterious blonde hair—remain in the episode that made it to air. After massive re-shoots, re-castings, and essentially constructing a new episode out of the ashes, Weiss and Benioff managed to score a hit. We may never get to see the full, original pilot, but in a new interview we have a better sense of why it was so awful.

John August (Go, Big Fish, and several other Tim Burton projects) and Craig Mazin (The Hangover sequels and Identity Thief) are screenwriters and, in Mazin’s case, personal friends of Weiss and Benioff. The pair also host a podcast called Scriptnotes, which this week had the Game of Thrones show-runners on to talk about the pilot. Mazin actually saw the original pilot directed by Tom McCarthy of Spotlight, The Station Agent, and The Visitor fame and, along with a few friends, was asked to offer his opinion.

“Watching them watch that original pilot was one of the most painful experiences of my life,” Weiss said on the podcast. “As soon as it finished, Craig [Mazin] said, ‘You guys have a massive problem.’” Was it the flashback to Ned’s brother dying that was the issue? Jennifer Ehle’s original performance as Catelyn Stark? The “lunatic,” overwrought death of Jon Arryn? Or maybe it was the fact that, according to Benioff, “none of (our friends) realized that Jaime and Cersei were brother and sister, which is a major, major plot point that we had somehow failed to establish.”

Actually it was all of that. “I was taking notes,” Benioff says, “and I had this yellow legal pad, and I just remembered writing in all caps, ‘MASSIVE PROBLEM,’ and it’s all I could think about the rest of the night. Craig didn’t really have any great ideas except that he said ‘change everything.’”

Change everything they did. Though some original footage remains—for example, you never see Sansa and Catelyn in the same frame because they just inserted Michelle Fairley’s footage to cover Ehle’s old performance—Weiss and Benioff re-shot about 90 percent of the pilot. Tom McCarthy didn’t even wind up with his name on the final product. That credit went to Timothy Van Patten, who also directed the second episode. McCarthy has said: