The Justice League of America first faced Starro The Conqueror in The Brave And The Bold #20, first published on December 29, 1959.
Season 4 of The Flash has centered upon the battle between Team Flash and Clifford DeVoe – a.k.a.
An Easter egg in “Subject 9” – the latest episode of The Flash – makes reference to the very first battle fought by the Justice League of America in their first comic book appearance.
Sadly, it seems unlikely we’ll get to see Team Arrow or Team Flash face down telepathic alien starfish anytime soon.