Actress Danielle Panabaker who will play Caitlin Snow aka Killer Frost and actor Carlos Valdes who will play Cisco Ramon aka Vibe on the pilot of The Flash television series, will both appear on the upcoming “The Man Under the Hood” episode of Arrow. It will be the 19th episode of the second season.
Executive producer Marc Guggenheim confirmed the news earlier today.
— Arrow – GreenArrowTV (@GreenArrowTV) March 17, 2014
Green Arrow TV also confirmed that Barry Allen would not returned to the episode because he still has not recovered from the lightning strike. It is still uncertain if the two characters will appear as their costume alter egos or not but it is still exciting non the less to see that characters from both shows are appearing in the show.
As a fan of Arrow, I am excited to see this shared universe continuing leading up to the pilot episode of The Flash. Let us hope that we might get to see our first appearance of the two characters in their respective costumes.
Source: Green Arrow TV Twitter page