"'What's Past is Prologue' takes viewers on a Flash-tastic journey back in time with a series of flashbacks that make for an eventful, charming, and commemorative 100th episode." Jesse Schedeen of IGN gave the episode a rating of 6.7/10, with the verdict being "As exciting as it is to see The Flash celebrate its 100th episode, [it] didn't fully realize its potential. The time travel premise worked whenever the focus remained on Harrison Wells, but too much of this material played out as if Barry and Nora were watching a clip show of past seasons." Notes References External links 2018 American television episodes The Flash (2014 TV series) episodes Television episodes about time travel