As mentioned, one of the funnier moments of Potential Energy was the gag that everyone bar Barry already knew about the Turtle. However, another throwaway line in there was about Cisco keeping tabs on a list of metahumans that Barry hasn't come across yet. That there are metahumans out there shouldn't really come as a big surprise, but it is interesting to think that Cisco already knows about them - and has probably given them names, if they've displayed their powers at least. It makes me wonder just who else could be on the radar for an appearance. Before Season 2 started, names like Mirror Master and Doctor Alchemy were mentioned pretty heavily, so could we soon be seeing these show up in Central City (Mirror Master in particular is one that would be great to see on the show).