On Earth-2, Robert Queen being the Green Arrow instead of Oliver Queen (who died instead of him) mirrors to some degree the story in the comic book crossover "Flashpoint." In the story, Barry Allen goes back in time to save his mother from being killed by the Reverse-Flash and ends up changing history. In the alternate timeline, Barry discovers that Bruce Wayne's father, Thomas Wayne, is Batman. Bruce died instead of his parents and Thomas Wayne instead took up the mantle of the Batman. The writer of "Flashpoint" was Geoff Johns, who has worked on both Arrow (2012) and The Flash (2014).
In the scene where Patty Spivot is talking to Joe West about Doctor Light's ability to control light, she explains that light can be manipulated to create "hard light". This may be a reference to the Lanterns who use the power of their rings to create hard light constructs.
At 14:20 a woman in a tan jacket and slacks descends the steps in front of the Central City Police station. She is holding a mobile phone to her left ear. This brief scene appears in almost every episode of the Flash. Watch for it.
When Dr. Wells watches the news on Earth-2, the channel's number is 52, a possible reference to the new 52 stories.