The name of Oliver's club is Verdant, which means "green with vegetation; covered with green growth", which is befitting as the Hood's outfit is green. The logo also resembles an arrow head.
Oliver mentions having dated Steve Aoki's sister, one of whom is Devon Aoki, who was originally cast as Tatsu Yamashiro/Katana in season 3 but was later replaced by Rila Fukushima.
While at the hospital after saving Thea, Roy Harper mentions how he doesn't like needles. In the comics, however, in 1971 Roy was addicted to heroin and was featured on the cover of "Green Lantern" Vol 2 #85 having just shot up with the needle still laying next to him in an award winning story arc By Dennis O'Neil and Neal Adams. Neal Adams also produced the art.
The outfit Helena Bertinelli/The Huntress wears in the strip club at the beginning is a reference to the costume the character wears in the original comic book.
Roy mentions being afraid of needles. While this is a contradiction to his character's usual characterization, the actor, Colton Haynes, is actually terrified of needles in real life.