He was first introduced as Barry Allen (Grant Gustin) in season two, episode eight of Arrow titled ‘The Scientist’. He goes to Starling City to investigate a break-in carried out by somebody who was really strong. Barry comes into contact with Oliver Queen (Stephen Amell) when an industrial centrifuge is stolen from Queen Consolidated Applied Sciences Division. The man who stole it was able to rip out off the ground. Barry helps Team Arrow find the thief. The episode ended with Barry heading back to Central City but is then abducted and bought to Team Arrow’s headquarters because Oliver had gone out being the vigilante and almost gotten himself killed…again. They needed Barry’s help to save Oliver from certain death.
Skipping ahead. After the season two finale, Arrow writers said that there would be a Flash spinoff series but in the same universe as Arrow. The fandom exploded. All we need now is a television adaptation of Batman. Then we would be half way to having the Justice League. Imagine that, a live action, television adaptation of the Justice League. That would be heaven.
In the summer of this year, the pilot episode of The Flash leaked online and in October, it was officially aired on television. Barry is famous for being late but then makes up for it by telling his bosses what they need to hear. He is ridiculously smart. He can tell a car’s make and model by looking at its tire tracks. His superpower isn’t being fashionably late. He was hit by a bolt of lightning which passed through a storm cloud created when a particle accelerator exploded during an experiment at S.T.A.R Labs at the same time as a lightning storm. The lightning struck Barry in his lab with all his chemicals in his immediate proximity. He was put into a coma for nine months and then he woke up, oblivious to the fact that others had been hit by the same cloud that hit him. There were people like him out there, in Central City with special abilities like him. S.T.A.R Labs decided to call these individual people metahumans.
The first three episodes were Barry finding and defeating metahumans effected by the particle accelerator explosion. The first was called Clyde Martin/Weather Wizard, the second was called Danton Black/Multiplex and third was Kyle Nimbus/The Mist. Nimbus is a renowned Flash villain and episode four introduced us to famous Flash villain, Leonard Snart/Captain Cold (Wentworth Miller,Prison Break). Arrow character, Felicity Smoak (Emily Bett Rickards) also featured in this episode, helping S.T.A.R Labs and The Flash to defeat Captain Cold.
The final minutes of episode four introduced us to another villain. I believe him to be Mick Rory/Heatwave. Captain Cold & Heatwave are famous for working together in the comics. At the end of the episode says “So do you still like playing with fire? You’re gonna love this. Are you in Mick?” then the anonymous person says “Yeah buddy. I’m in” He even says “Mick.”