Some things simply aren't meant to be messed with, and the timeline is one of them, as Barry Allen is about to find out.

In a recent interview with Entertainment Weekly, "The Flash" Executive Producer Andrew Kreisberg spoke at length about the effects of Barry's repeated alterations to the timeline, and how some of those changes, are permanent.

While Season 3's opening story arc, "Flashpoint," is only expected to last a few episodes, the effects of it, will be season-long. "There will be consequences that last throughout the season, and quite frankly, last throughout the series," Kreisberg said. "That's one of the things that we're attempting to do is have the pitfalls of time travel be long-lasting and that some things can be fixed, and then some things are broken forever."

Memories will be lost and replaced by new ones, leading star Grant Gustin's character to the proverbial fork in the road, where he realizes "he may have traded his happiness for his friends."

"He begins to see that the cost of him getting his happy ending might be too much to bear," Kresiberg teased.

Another unintended consequence of saving his mother at the end of Season 2? The return of his arch-enemy, the Reverse-Flash.

"Barry has messed with the universe to find his happy ending," Kreisberg explained, "and he’s put in the awkward and ironic position of having his greatest villain, the man who killed his mother, being the one to tell him, 'This is wrong, you’re a hero and heroes don’t do this.' It's a great way to have him interact with his singular greatest foe by having the villain essentially be on the side of the angels and be right."

"The Flash" returns for Season 3 Oct. 4 on The CW.