Time travel is implied right from the first episode of the CW’s rendition of The Flash where a newspaper from the future is seen in the closing scene. The rest of the first season builds a fine time-travel arc that includes a nefarious time traveler from the far future, a classic grandfather paradox with a twist (sadly not examined), a do-over day for the Flash (which Harrison Wells calls “temporal reversion”), and a final episode that sees the Flash travel back to his childhood (as well as a hint that Rip Hunter himself will soon appear on the CW scene).