The Android Flash looks like Zoom, the Reverse Flash from the comics.
During a crowd scene, a blonde man in a tan trenchcoat can be seen to the right-hand side of The Atom. This resembles John Constantine, from the Hellblazer and Swamp Thing comic book series.
To counter his alter ego's haunting message about his not being good enough for the Justice League, Flash retorts that he will paint his name on his conference-table seat, an in-joke for the comics where the Justice League's conference table was set up with chairs whose backs each had the insignia of the member they belonged to.
Amongst the Justice League members in the crowd, we also see: Lois Lane, Jimmy Olsen, Snapper Carr, and Summer Gleason.
Dwayne McDuffie stated that in the first draft of this episode, Clark was going to reveal his identity to Lois. however, they were explicitly told not to do it. Bruce Timm has gone on record to support the final product.