One major change from the book to the television show involves how far into the future people see when they back out.

"We've obviously changed it from 21 years to six months," said Guggenheim. "The real appeal when you are doing a television series is getting to see the payoff of when the future becomes the present. David and Brannon made the decision to have that payoff come in the first season."

One aspect of the show that has people talking is the high caliber of its cast. Flash Forward features Joseph Fiennes, John Cho, Jack Davenport and Courtney B. Vance. That cast was one of the factors that intrigued Guggenheim.

"I wish I could take credit for the cast," he said, "but I got involved after the cast was put together."