Over the course of six seasons, The Flash slowly came to focus Caitlin Snow’s storylines around her Killer Frost persona rather than her love life. This was apparently the result of the writers responding to actress Danielle Panabeker’s growing dissatisfaction with her role and fan jokes about the show’s writing becoming predictable after the first three seasons.
Dr. Caitlin Snow was introduced into the Arrowverse in the season 2 Arrow episode “The Man Under The Hood,” as a STAR Labs employee who was clearing out the inventory of their Starling City site when it was burglarized by Deathstroke. She was later brought into The Flash series and revealed to be the medical doctor who had cared for Barry Allen while he spent nine months in a coma after being struck by lightning on the night the STAR Labs particle accelerator exploded. Beyond helping Barry to master his super-speed powers and protect Central City from the rising threat posed by metahuman criminals, Caitlin’s story in season 1 largely centered around her mourning her fiancee Ronnie Raymond, who apparently died in the particle accelerator explosion, then her searching for him after it became clear that Ronnie was the mysterious “Burning Man” seen around Central City. The two married in The Flash‘s season 1 finale but their happiness was short-lived, as Ronnie sacrificed himself in The Flash‘s season 2 premiere to close a wormhole that threatened the world.
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