Kevin Smith first foray into The Flash was last season with episode ?The Runaway Dinosaur.? Now he?s back with seventh episode of The Flash Season 3. The episode features villain Killer Frost the metahuman double of Barry Allen?s compatriot, Caitlin Snow (played by Danielle Panabaker) "I start shooting my second episode of @CW_TheFlash today," Tweeted Kevin Smith. Though this episode's title shares a name with the villanous doppelgänger, some mystery surrounds the supposed appearance of character Killer Frost.