Andy Mientus, the actor who portrays Hartley Rathaway/Pied Piper, auditioned for the role of Barry Allen/The Flash, but lost to Grant Gustin.
During the press conference, Dr. Wells says that he failed the city. "You have failed this city" is what the Arrow says to criminals before he takes them down in Arrow.
Hartley Rathaway's technology is similar to that of the Canary's cry technology seen in Arrow (2012).
In the new 52 comics, Hartley Rathaway/Pied Piper is a reformed criminal and the romantic partner of Director David Singh.