This is a crossover episode with Legends of Yesterday (2015) (Arrow season 4, episode 8) as a back-door pilot for the spin-off series DC's Legends of Tomorrow (2016).
Cisco calls The Flash "Barry" in front of Kendra. This is the third time he's made that mistake.
The song heard when Kendra's power manifest is eventually used as the theme for Legends of Tomorrow.
Hawkman debuted in Flash Comics #1 (1940). Shiera Saunders, the character on whom Kendra Saunders is based, debuted in the same issue but did not don a superhero identity until All-Star Comics #5 (1941), three issues before the debut of Wonder Woman.
In the first Flash/Arrow crossover, the Flash episode had the Arrow team visiting Central City, and the Arrow episode had the Flash team visiting Star City. In this crossover, the Flash episode takes place in Star City, and the Arrow episode takes place in Central City.