History Recap / TheFlash2014S5E8WhatsPastIsPrologue

** Ralph plays "[[Film/BackToTheFuture Back in Time]]" when Nora and Barry time travel, much to the team's annoyance.

* AllForNothing: The plan to counter Cicada's dagger fails when Cicada is able to summon enough willpower to call it back from '''''[[UpToEleven friggin' space]]'''''.

* AbsenteeActor: Joe & Cecile, although Joe appears via stock footage.

* CallForward: Before launching the Particle Accelerator, Thawne told Cisco that he had vibes that Cisco's future would be great.

* SequencingDeception: This episode revisits one of the flashbacks from "[[Recap/TheFlash2014S1E3ThingsYouCantOutrun Things You Can't Outrun]]" and retroactively makes it an example of this trope. In the original episode Wells activated the accelerator right after saying "I feel like I've waited for this day for centuries", and after turning it on he popped open a bottle of Dom Pérignon. This episode shows that after saying this but before turning on the accelerator, he paused because he sensed the presence of Barry and Nora. He walked into the hall to investigate whether they were in the Time Vault, but Cisco and Caitlin came to check on him, and as somewhat of a distraction he asked Caitlin to go get the bottle of Dom they'd been saving. Judging by this, and by the fact that if Barry and Nora hadn't [[YouAlreadyChangedThePast already changed the past]] many of the victims of the accelerator [[ForWantOfANail would be completely different as a result of the two-minute time difference of the explosion]], it's implied that Barry and Nora had always been there, meaning "Things You Can't Outrun" just skipped over the two extra minutes that were shown in this episode.

* TheBusCameBack: Plenty of characters fitting the 100th episode, including Zoom (with both Tony Todd and Teddy Sears returning), a Time Wraith, Gideon, Grodd (before he became a meta), Harry Wells, Nora and Henry Allen, and of course Eobard Thawne (in his Wells disguise). Hartley Rathaway, The Mardon Brothers, Ronnie, the [=DeVoes=], and Dr. Stein appear via stock footage. Morena Baccarin also recorded new lines as the original Gideon after ''Legends of Tomorrow'' opted to use another actress, and is even confirmed to still be around in the present.

* {{Adorkable}}: Thawne and Cisco attempting a handshake, which trails off when they can't figure out whether to do a traditional one or a fist bump. After a few moments, they awkwardly decide to just go back to what they were doing.

* SequencingDeception: A retroactive example, with this episode revisiting one of the flashbacks from "[[Recap/TheFlash2014S1E3ThingsYouCantOutrun Things You Can't Outrun]]". In the original episode Wells activated the accelerator right after saying "I feel like I've waited for this day for centuries", and after turning it on he popped open a bottle of Dom Pérignon. This episode shows that after saying this but before turning on the accelerator, he paused because he sensed the presence of Barry and Nora. He walked into the hall to investigate whether they were in the Time Vault, but Cisco and Caitlin came to check on him, and as somewhat of a distraction he asked Caitlin to go get the bottle of Dom they'd been saving. Judging by this, and by the fact that if Barry and Nora hadn't [[YouAlreadyChangedThePast already changed the past]] many of the victims of the accelerator [[ForWantOfANail would be completely different as a result of the two-minute time difference of the explosion]], it's implied that Barry and Nora had always been there, meaning "Things You Can't Outrun" just skipped over the two extra minutes that were shown in this episode.

* AndThenWhat: Barry’s response to Cicada saying he'll kill all the Metas is to ask "What about you?" Cicada says he'll "join" the other Metas when he's done.

* CripplingOverspecialization: It's revealed Cicada's dagger only nullifies the powers of metahumans if their powers came from Dark Matter. Normally, this wouldn’t be a problem, but more metahumans with other sources are coming up.

* SequencingDeception: A retroactive example, with this episode revisiting one of the flashbacks from "[[Recap/TheFlash2014S1E3ThingsYouCantOutrun Things You Can't Outrun]]". In the original episode Wells activated the accelerator right after saying "I feel like I've waited for this day for centuries", and after turning it on he popped open a bottle of Dom Pérignon. This episode shows that after saying this but before turning on the accelerator, he paused because he sensed the presence of Barry and Nora. He walked into the hall to investigate whether they were in the Time Vault, but Cisco and Caitlin came to check on him, and as somewhat of a distraction he asked Caitlin to go get the bottle of Dom they'd been saving. Judging by this, and by the fact that if Barry and Nora hadn't [[YouAlreadyChangedThePast already changed the past]] many of the victims of the accelerator [[ForWantOfANail would be completely different as a result of the two minute time difference of the explosion]], it's implied that Barry and Nora had always been there, meaning "Things You Can't Outrun" just skipped over the two minutes that were shown in this episode.

** Cicada's dagger would have left a crater and created a big impact from being recalled from space.

* GodzillaThreshold: Zoom's Speed Force Transmitter is broken, forcing Barry and Nora to turn to Eobard Thawne for help to fix it. Also, from the viewpoint of Thawne, he only helps them because he learns they want to use the device to stop Cicada.

* WhereItAllBegan: Overlaps with WhenItAllBegan due to the time-travel element. Barry and Nora go back to the day Barry's story began - when the Particle Accelerator exploded. At the end of the episode, they also travel back to the night of Nora Allen's death, albeit hours before the crucial events.

** Before that, he also tries to guess who she is. Among the guesses are Jesse Chambers, Libby Lawrence and Danica Williams.

* WhamEpisode: Nora is in the past on somebody else's orders... Eobard Thawne's.

** According to Gideon, Nora AKA XS becomes a member of the Legion of Superheroes, much like the comic-book XS did. Moreover, Gideon specifically mentions that it's a 'rebooted' Legion, a sly reference to the fact that XS was introduced in the comics during the first reboot of the Legion of Superheroes franchise.

* StartOfDarkness: Dr. Ambres began when the Particle Accelerator exploded.

* VillainousBreakdown: Thawne has one when Barry tells him he won't be going back to his time... [[BlatantLies unless he helps fix the Speed Force transmitter]].

* TheBusCameBack: Plenty of characters fitting the 100th episode, including Zoom (with both Tony Todd and Teddy Sears returning) and of course Eobard Thawne (in his Wells disguise), a Time Wraith, Gideon, Grodd (before he became a meta), Harry Wells, and even Nora and Henry Allen. Hartley Rathaway, The Mardon Brothers, Ronnie, the [=DeVoes=], and Dr. Stein appear via stock footage. Morena Baccarin also recorded new lines as the original Gideon after ''Legends of Tomorrow'' opted to use another actress, and is even confirmed to still be around in the present.

* WhamEpisode: Nora is in the past on somebody else's orders...Eobard Thawne's!

* BerzerkButton: Thawne does not take well Barry flatly telling him that no matter what happens, Thawne never gets back to the future.

* BezerkButton: Thawne does not take well Barry flatly telling him that no matter what happens, Thawne never gets back to the future.

* {{Futureshadowing}}: When Barry and Nora go back to the night of the Particle Accelerator explosion, we see Thawne-as-Welles offer his hand to Cisco for a shake, which strongly resembles the way he would later kill Cisco in an alternate dimension.

* TheBusCameBack: Plenty of characters fitting the 100th episode, including Zoom (with both Tony Todd and Teddy Sears returning) and of course Eobard Thawne (in his Wells disguise), a Time Wraith, Gideon, Grodd (before he became a meta), Harry Wells, and even Nora and Henry Allen. The Mardon Brothers, Ronnie, the [=DeVoes=], and Dr. Stein appear via stock footage. Morena Baccarin also recorded new lines as the original Gideon after ''Legends of Tomorrow'' opted to use another actress, and is even confirmed to still be around in the present.

* VillainousBreakdown: Thawne has one when Barry tells him he won't be going back to his time... [[BlatentLies unless he helps fix the Speed Force transmitter]].

* BrickJoke: After ''five'' seasons, Cisco has finally achieved his ambition of making Barry his very own Flash ring.

* VillainousBreakdown: Thawne has one when Barry tells him he won't be going back to his time.