Over a decade ago, "Glee" actor Grant Gustin guest starred on an episode of the successful but fledgling CW series "Arrow," throwing Stephen Amell's Emerald Archer together with an awkward ...

Morena Baccarin played a key role opposite Grant Gustin in The CW's The Flash TV show (although the Deadpool veteran certainly didn't look like herself).

It would have been hard to believe at the time that their meeting would not only lead to "The Flash" — a wildly popular series in its own right that immediately matched pace with "Arrow" in a standout ...