Oliver sometimes refers to his sister Thea as "Speedy", a nickname she earned by constantly chasing after him as children. In DC Comics, "Speedy" is the name of two superheroes that have each served as teen-aged sidekicks for the Green Arrow (a.k.a. Oliver Queen), possibly foreshadowing things to come in the series.
In the beach scene where Queen is rescued, a mask similar to the one worn by DC character Deathstroke can be seen. An arrow can be seen protruding from the right eye of the mask; this is the same eye that the character lost in the comics.
The character of John Diggle is named after the writer of The Green Arrow's revival comic "Year One", Andy Diggle.
The Hatley Castle used for the Queen Mansion outdoor shots is in Colwood, British Columbia. It was also used for exterior shots of the main characters' Legacy headquarters in the television series Poltergeist: The Legacy (1996).
It is also used for Xavier's School for Gifted Youngsters in the X-Men movies as well as the Luthor Mansion in the television show Smallville (2001) and also in the television show Supernatural, as several places throughout that shows run.
Moira & Thea have a mole in almost the same spot on their upper lip.