Arrow: 18 Easter Eggs, In-Jokes And References You Need To See
Arrow may not have metahumans, but it clearly has metahumour.
Harley Quinn was teased during the Suicide Squad episode in season 2, causing a ridiculous amount of excitement at the possibility of a proper appearance on the show.
That dream was quickly crushed though when it was revealed that higher-ups had blocked the move, due to her appearances in next years Suicide Squad film, with Margot Robbie playing the character.
However, shes still alluded to in season 3, with Cupid fulfilling her role as the crazy member, and her relationship with Deadshot is similar to that of him and Harley in the comics. Oliver also makes reference to the Squads previous unhinged female member. Its a nice wink to what couldve been, if only Warner Bros. would learn to share.