what are the superpowers of this character?
He has the power to move at superhuman speeds.
The Flash (2014 TV series)
 It is based on the Barry Allen incarnation of DC Comics character the Flash, a costumed superhero crime-fighter with the power to move at superhuman speeds. 
when did the flash first appear on arrow UNANSWERABLE what is the premise of the above mentioned show? A crossover between the two series was announced in July 2014, after Barry Allen had been introduced in "Arrow"s second season ahead of the debut of "The Flash" who is the this aforementioned character that appears on the show? He is an American superhero television series.
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The Flash (2014 TV series) [SEP] Introduction
The Flash is an American superhero television series developed by Greg Berlanti, Andrew Kreisberg, and Geoff Johns, airing on The CW. It is based on the Barry Allen incarnation of DC Comics character the Flash, a costumed superhero crime-fighter with the power to move at superhuman speeds. It is a spin-off from "Arrow", existing in the same fictional universe known as Arrowverse. The series follows Barry Allen, portrayed by Grant Gustin, a crime scene investigator who gains super-human speed, which he uses to fight criminals, including others who have also gained superhuman abilities. Initially envisioned as a backdoor pilot, the positive reception Gustin received during two appearances as Barry on "Arrow" led to executives choosing to develop a full pilot to make use of a larger budget and help flesh out Barry's world in more detail.