- "Oliver died for more than this Earth's survival. Oliver laid down his life so the people he loved could live theirs. That includes you. Life's a marathon, not a sprint, Barry. Slow down and enjoy it."
- —John Diggle to Barry Allen
After The Citizen prints an explosive story, Iris's life is threatened. Refusing to hide from those that are attacking her, Iris sets out to expose a dangerous organization. Meanwhile, Barry must face the consequences of the Crisis and fulfill Oliver Queen's wish for him.
- Grant Gustin as Barry Allen/The Flash
- Candice Patton as Iris West-Allen
- Danielle Panabaker as Dr. Caitlin Snow/Frost
- Carlos Valdes as Cisco Ramon
- Hartley Sawyer (credit only)
- Danielle Nicolet as Defense Attorney Cecile Horton
- Tom Cavanagh as Harrison Nash Wells and Harrison Wells (footage)
- Jesse L. Martin as Captain Joe West
Special guest star
- Victoria Park as Kamilla Hwang
- Kayla Compton as Allegra Garcia
- Eric Nenninger as Joseph Carver
- Emmie Nagata as Dr. Kimiyo Hoshi/Doctor Light
- William MacDonald as Gene Huskk
- Tess Atkins as Natalie
- Eduard Witzke as Sterling Brooks
- Andrew J. Hampton as Maurice
- Gary Starkell as Riggs Wellington
- Emmett Lee Stang as Mystery Man
- Arran Henn as CatCo Reporter
- Sonia Beeksma as KPJT Reporter
- Jarryd Baine as Channel 52 News Reporter
- This episode takes place before the events of "".
- This episode introduced a new title card which contains a montage of different characters, similar to the one from Smallville.
- Cisco made a board with a drawing of the world map which shows important locations from the DC Universe including:
- United States: Star City, National City, Gotham City, Central City, Metropolis, Freeland
- Central America: San Monte, Santa Prisca
- South America: Corto Maltese
- Europe: Markovia, Kasnia
- Asia: Qurac, Nanda Parbat, Tokyo
- Africa: Zambesi, Tunisia, Gorilla City
- Pacific Ocean: Kooey Kooey Kooey Island, Dinosaur Island, Lian Yu
- The Arctic: Fortress of Solitude
- Cisco made a timeline of Earth-Prime which went over important events and hero debuts including:
- 2000: The murder of Nora Allen.
- 2003: Kara's pod lands on Earth.
- 2005: J'onn J'onzz becomes Hank Henshaw.
- 2007: Oliver Queen is stranded on Lian Yu.
- 2008: Slade Wilson is injected by Mirakuru.
- 2009: Hong Kong is hit by the Alpha-Omega virus, Black Lightning retires from vigilantism.
- 2012: The Hood debuts in Starling City.
- 2013: The Undertaking occurs.
- 2014: The particle accelerator explodes. Slade invades Starling City with his Mirakuru army. Barry wakes up from his coma and becomes The Flash. John Diggle, Jr. and Sara Diggle are born.
- 2015: Bruce Wayne leaves Gotham City. Supergirl debuts in National City. Rip Hunter recruits the Legends.
- 2016: Flash and Supergirl team up. Zoom invades Central City. The Dominators invade Central City.
- 2017: Barry and Iris's wedding is interrupted by time travelling Nazis. The Ray debuts
- 2018: Batwoman debuts. Black Lightning returns. Thunder debuts. President Marsdin is exposed as an alien.
- 2019: The Crisis begins.
- 2020: The heroes return and defeat the Anti-Monitor.
- Cisco has made a "Who's Who" binder of those whose status upon Earth-Prime's formation are unknown. The following appear in it:
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