6) Flash Back (Season 2, Episode 17)
Speaking of which, the spectre of Eobard Thawne heavily hangs over our hero in season 2 – which makes it all the more dramatic when Barry goes back in time to get his old enemy’s help with stopping Zoom.
While we’ve nothing against Matt Lescher’s portrayal of the real Reverse-Flash, Tom Cavanagh’s fake Harrison Wells is the one we love the best. As such, it was great fun to see that version of the character return, by going back to when he was still pretending to be Barry’s wheelchair-bound mentor. There are also some welcome appearances from poor dead Eddie and a reformed Pied Piper.
Returning to the timeline of season 1 was a brilliant story device and, in retrospect, the episode is even sharper as it foreshadows Barry’s much bigger alteration of the timeline at the end of the season.