He was Campbell Price on 90210 and a Warbeler on GLEE is now the new FLASH.
"Barry Allen" was introduced on Arrow near the end of their second season. Naturally, we meet the endearing Barry Allen who is of the science nature. Definitely, perfect for Felicity Smoke (Emily Bett Rickards).
Seriously, Arrow certainly jump started THE FLASH by letting us in on "Barry Allen".