Both of those character names have significance to fans of the DC Comics source material. "Eddie Thawne" appears to be the show's take on "Eobard Thawne," Barry Allen's archrival Professor Zoom. "Caitlin Snow" is the latest version of DC villain Killer Frost, who debuted in the "Killer Frost" one-shot as part of Sept. 2013's "Villains Month."
Deadline describes Eddie Thawne as, "a recent transfer to the Central City Police Department, whose past is a mystery and who harbors a dark secret;" and Caitlin Snow as, "a highly intelligent bioengineering expert who lost her fiancé during an explosion at S.T.A.R. Labs."
"We're using a lot of mythology, a lot of characters from the comics in the development of the 'Flash' show," DC Entertainment chief creative officer and former "Flash" comic book writer Geoff Johns said in December. "I don't want to get too specific yet, but you'll see a lot of characters, a lot of elements from that. It's very much 'The Flash.'"
Cosnett has recently been seen on another CW program, "The Vampire Diaries," as Dr. Wes Maxfield. Panabaker has appeared on "Necessary Roughness" and "Bones." The two join Grant Gustin, who debuted in the title role of Barry Allen/The Flash in two episodes of "Arrow" last month, and Jesse L. Martin, announced earlier this week as playing "Detective West."
"The Flash" pilot, in contention for a spot next season on The CW, was written by Johns and "Arrow" executive producer Greg Berlanti and Andrew Kreisberg. David Nutter, known for an impressive track record with successful pilots (including "Arrow"), will direct.