Marathon

Synopsis
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.

Starring

 * 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

 * David Ramsey as John Diggle

Guest starring

 * 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

Co-starring

 * 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

Trivia

 * This episode introduced a new title card which contains a montage of different characters, similar to the one from Smallville
 * Similar to his Earth-90 counterpart over on The Flash, Barry Allen receives a gift of the mask of his vigilante mentor. Being Desmond Powell and Oliver Queen respectively.
 * Despite coming out after the Arrow series finale, this episode takes place before
 * The scene where Barry and Diggle are talking about Oliver is very similar to the scene from Spider-Man Far From Home where Peter Parker and Happy Hogan talk about Tony Stark in Avengers Endgame.
 * 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, Toyko
 * 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 is 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. The Ray debuts
 * 2017 Barry and Iris's wedding is interrupted by time travelling nazi clones.
 * 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.