Via AOL:

“It wasn’t a retooling of the show,” Mitchell explained. “I read the [original] script and the rewrite of the script. Retooling can have any definition. What exactly happened was that they [ABC] didn’t think that the pilot would be as well received as it was, and when it was they got really excited and just wanted to bump everything up. So everything that we have gone back to reshoot has been to bump up the action, bump up the gadgets, bump up the effects, bump up the drama and move people closer together to make things more scary and tenuous. Instead of slowly reeling people in, they’re just doing it a little bit faster.”

Mitchell added that the characters and actual scenes have not changed, it’s just that the intensity has increased. “There was this new technology that came into it because they wanted to keep it going,” she reported. “We start out episode 2 with some really crazy stuff that’s probably my favorite, and there is one [thing] in episode 4 where I was like, ‘Yeah!’ Just as a sci-fi fan. We reshot stuff for every episode, but we didn’t change the heart of any of the scenes. We just amped it up. I can tell you that I did a lot more running in the reshoots than I did [originally].” With a laugh, she concluded, “I’m now running and hitting things quite a lot, and I think that was their intention.”