The episode was written by Katherine Walczak from a story by Greg Berlanti and Andrew Kreisberg, and directed by Millicent Shelton.
Grant Gustin stars as Barry, and is joined by principal cast members Candice Patton, Danielle Panabaker, Carlos Valdes, Keiynan Lonsdale, Tom Cavanagh, and Jesse L. Martin.
The episode sees Barry, Cisco Ramon and Harry Wells travel to the parallel universe Earth-2 to rescue Harry's daughter Jesse from Zoom, while back on Earth-1, Jay Garrick takes over Barry's crime fighting duties when the metahuman Geomancer attacks Central City.
After seeing his doppelgänger, a non-metahuman forensic scientist, on the news, Barry abducts and renders him unconscious to impersonate him and obtain more information on Zoom.
Earth-2's versions of Caitlin Snow and Ronnie Raymond, known as Killer Frost and Deathstorm respectively, are working for Zoom and realize that some breachers have entered Earth-2.
Jay refuses and reveals to Caitlin that he invented Velocity-6 and previously took it to become faster but the side effects caused his loss of speed and are gradually killing him.
Cisco, who has made a weapon to combat Frost, attempts to stop the pair, but is confronted by his own doppelgänger, known as Reverb, who is also working for Zoom and can manipulate sonic vibrations to create powerful shock waves.
Barry later awakens in a glass cell at Zoom's lair, where there are two other prisoners; Jesse and a man trapped in an iron mask.
[2] The episode, which was the season's thirteenth, was directed by Millicent Shelton and written by Katherine Walczak, Greg Berlanti and Andrew Kreisberg.
"[5] Examples include the fact that Barry Allen is not a metahuman; Iris West is a police detective married to him;[6] Caitlin Snow, Ronnie Raymond and Cisco Ramon are the metahuman criminals Killer Frost, Deathstorm and Reverb respectively;[7] Joe West is a lounge singer who goes by Joseph and dislikes his son-in-law;[8] Nora Allen is alive;[9] David Singh is a criminal; Henry Hewitt is not a metahuman; and Floyd Lawton is a police officer with poor marksmanship skills.
Season two co-showrunner Aaron Helbing said these were purely "just Easter eggs for fun",[7] with Todd saying those names were chosen from a "giant board of probably 50 ideas".
[14] Additionally, Robbie Amell, Demore Barnes, Michelle Harrison, Michael Rowe, and Patrick Sabongui reprise their roles as Earth-2 versions of Deathstorm, Henry Hewitt, Nora Allen, Floyd Lawton, and David Singh, respectively.
The website's critical consensus read at the time, "Invigorated by a jolt of out-of-this-world fun, 'Welcome to Earth-2' successfully ups the pace and action, while providing plenty of delightful Easter egg moments throughout.
"[28] Angelica Jade Bastién of Vulture praised the direction, action sequences, and the cast's performances, particularly of Gustin and Patton.
"[31] Ed Gross of Empire rated the episode four stars out of five, saying, "The Flash may hit an occasional speed bump (sorry) along the way, but it pretty consistently delivers the goods.
"[12] Charlie Hall of Polygon gave the episode a mixed review and despite complimenting the premise, said, "it eventually devolved into the same storyline we keep seeing over and over again.