The character Curtis Holt (Echo Kellum) was introduced in the fourth season of TV show Arrow as an employee of Palmer Tech, a company headed by Felicity Smoak (Emily Bett Rickards) who is part of Team Arrow.
Since Curtis is really good at his job as the hardware tech guy, Felicity occassionally ropes him in to help out with tech-related work. At the end of S4, Curtis had pretty much become part of the crew headed by Green Arrow (Stephen Amell), helping Felicity stop the nuclear bombs launched by the villain in a bid to destroy the world. In short, Curtis has the makings of a hero. As it happens, this character is based on DC’s Mister Terrific (who is known as Michael Holt in the comics).