Sara Lance says to a League assassin, "you should be mindful of your surroundings". Ra's Al Ghul, leader of the League of Assassins, says this to Bruce Wayne in Batman Begins (2005).
The bird Sara sees during this episode is a canary, referencing "The black canary" from the comics
Ron Selmour plays "The Butcher" here. He also appeared in Smallville episode Toxic (2008) in which he played the villain on the island where Oliver Queen was marooned.
First episode to show flashbacks following the Queen's Gambit sinking, from anyone's perspective other than Oliver's.