Characters Killer Frost and Vibe were implied in season 1 of "The Flash" and fans were even able to catch a quick glimpse of the former during the season 1 finale "Fast Enough" when Barry Allen was speeding through the fabric of space and time. According to a recent interview, the two might appear sooner than previously expected. 

DC All Access interviewed the cast of the show and when Danielle Panabaker was asked if fans would see Killer Frost in the near future, she simply replied, "You will see Killer Frost very soon, actually," implying that she might suit up as the super villain in season 2. 

Dr. Caitlin Snow, Panabaker's character in the series, doesn't seem like super-villain material but given that her fiance-turned-husband died once and came back as one-half of a fiery meta-human, there is room to argue that compounding problems might turn her to the dark side and eventually become the Killer Frost fans know from the comics. 

According to a report from Cinema Blend, it is also possible that Killer Frost might be from an alternate timeline where Caitlin is the one affected by the particle accelerator instead of Robbie. 

Cisco, played by Carlos Valdes, died in season 1 but was brought back when the Flash went back in time and altered the flow of events. However, instead of just forgetting what happened, Cisco still felt "vibrations" of the previous timeline and this was the first hint that his character may evolve into Vibe from the comic books. 

Vibe is an ally of the Flash and is capable of traveling through different timelines and dimensions at will. When asked if Vibe will also mark his appearance in season 2, Valdes stated, "I can say that some of the questions regarding the Vibe mythology will be answered. That's all I'm gonna say."

"The Flash" season 2 premieres this fall.