2015 is already set to be Marvel's biggest year yet. With the currently-airing Agent Carter proving to be a critical darling, Daredevil ready to introduce fans to the world of The Defenders in April and, of course, the summer pairing of The Avengers: Age of Ultron and Ant-Man primed to conquer the box office, there's no stopping their Cinematic Universe from expanding. As Agent Carter winds down, the promotion for the back half return of Agents of SHIELD's second season is beginning to kick into high gear. Being fans' weekly peek into the MCU, the show has come a long way from its early, pre-The Winter Soldier days of playing its cards close to its chest and has blossomed into an enjoyable beast standing on its own two feet. Though the adventures of Coulson and the gang have managed to introduce and incorporate many characters and concepts from the comics, including Glenn Talbot, Mockingbird and even Inhumans, it hasn't shied away from the MCU at large, ensuring that characters like Nick Fury, Maria Hill and Sif will always have a home when they're not being used in the films. At this point, it seems to be generally accepted that Marvel's top-line faces like Tony Stark, Thor, Bruce Banner and Captain America won't be popping in anytime soon. Despite that, the show still has huge potential ahead of it to give a number of existing film characters - and plot threads - who have either been underutilised or relatively forgotten about by the films the chance to show up and develop on the small screen. Even better, a number of these actors have histories with the small screen, making them seem far more amenable to showing up than Marvel's bigger stars. So with only one month to go until the Agents are back, let's take a spoilery look at 15 existing MCU faces that could realistically show up down the line for some time in the spotlight.