Vito D'Ambrosio reprises his role as Tony Bellows from The Flash (1990). While he was a uniformed Central City police officer in the earlier series, he is the Mayor of Central City in this version.
WWE Hall of Famer Adam "Edge" Copeland plays the Atom Smasher.
Weathersby & Stone is the name of the fictional law firm in Eli Stone (2008). Victor Garber played a role and Greg Berlanti was a writer for that series.
At 18:30 Cisco says "Sweet Sarek...". Sarek is the Vulcan father of Spock in the Star Trek universe.
The Flash Day scene, when Flash gets the key to the city, is a nod to the "Death of Superman" panel when we can see Lex Luthor looking at a scene where Superman gets the key to the city at Superman Day.