The first season's story arc dealt with "The Laughing Man", a cyber criminal who inspires a slew of copycat crimes. The hacker is capable of inserting his logo into people's minds so that the victim sees the image superimposed onto the real world. This logo becomes a dominant visual theme, and has even bled out of the show into the real world.
What I didn't know into more recently was that the logo was not crafted by the show's staff, but instead by british designer, TERRATAG. He was doing work for Frognation, a Japanese game developer and record label. He had sent over a bunch of stickers, and it happened that an employee at Frognation was also working on the production of the first season of the show. The director of the series, Kenji Kamiyama, saw the stickers, and sought out TERRATAG to create the design. You can read an interview with him about how he wound up involved with the production here. Also, you can find some great merchandise from TERRATAG here. Finally, If you want to bring the "Laughing Man" into the real world, pick up some stickers and put them over all of the faces of people in your photographs.
