20 Awesome DC TV Easter Eggs You Probably Missed
15. The Original Heroes (The Flash & Supergirl)
While Arrow might be a new addition to the live-action world of DC (in terms of his own standalone story, at least), both The Flash and Supergirl have been tried before. There was a Supergirl movie way back in 1984, aiming to capitalise on the success of the Superman movies around that time, and in the 90s there was a Flash TV series.
The stars of those, Helen Slater (Supergirl) and John Wesley Shipp (The Flash) have both appeared on their respective modern series, and have actually became the parental figures of the heroes they once played. Slater plays Eliza Danvers, the human foster mother of Kara, while Shipp plays Henry Allen, Barry's father.
Gotham has also got in on this action too, in a way, by having Paul Reubens reprise his role as the Penguin's father, which he first played back in Batman Returns. Sadly they haven't had Adam West make an appearance though (yet, anyway).