It's been a few years since the CW had a hit drama on their hands (The Vampire Diaries being the last), and Arrow has failed to disappoint viewers each week with the winning combination of action, mystery and mythology -- and an exceptionally good looking cast! The series may not have a huge cast, but these characters are as complicated as they come...
Oliver Queen/Arrow (Played by Stephen Amell)
Dating back to 1941, the Green Arrow has been a major character in the comic book series. Of all the superheroes, he is the only one to not possess an actual superpower. After being stranded on an island for five years, Oliver Queen was forced to fend for himself and stay alive amongst the most difficult conditions imaginable. No longer the billionaire playboy, Oliver has made it his personal mission to target all the names in his father's notebook in order to prevent Starling City from falling prey to the evil surrounding it. Oliver used to have a serious relationship with Laurel Lance, but his affair with her sister (who died aboard the yacht) put a major wrench in their relationship. Their chemistry is undeniable and I imagine as the series progresses, these two will wind up back together.
Laurel Lance (Played by Katie Cassidy)
The character of Laurel Lance is loosely based on the comic's Dinah, who was the daughter of the Black Canary. In Smallville, the character was named Tess Mercer. Laurel and Oliver had a serious relationship before he was stranded on the island for five years. Her father is a police detective and she is a lawyer, which comes in handy quite often for Oliver's various missions. While Oliver was missing, Laurel and Tommy (Oliver's best friend) had a relationship, but it's clear that she still has feelings for her first love.
Moira Queen-Steele (Played by Susanna Thompson)
Moira is Oliver's mother and unbeknownst to everyone she loves, a master manipulator and one of the people behind the sabotaging of the ill-fated yacht. We have yet to know who she is working for and what her motivation is, but one thing is clear - this woman cannot be underestimated. She loves her children, but not enough to keep them from harms way. Moira is married to Walter Steele.
Thea Queen (Played by Willa Holland)
Thea is Oliver's younger sister. Clearly deeply affected by the "death" of her brother, Thea continually acts out by getting drunk and sneaking out with her friends. The reappearance of Oliver in her life hasn't done much for her party girl ways, but slowly Oliver seems to be getting through to her.
John Diggle (Played by David Ramsey)
Diggle started out as Oliver's tough bodyguard, but several episodes in, he is let in on Oliver's big secret. Although at first horrified that Oliver is actually the vigilante stirring up trouble in Starling City, he eventually gives in and joins Oliver's crusade to save the city from evil. Using his military training, Diggle has proven to be almost as lethal as Oliver's alter-ego, Arrow.
Detective Quentin Lance (Played by Paul Blackthorne)
Laurel's father and Starling City's lead detective. Lance hates Oliver and blames him for the death of his daughter, who was aboard the yacht with him. Lance has made it his mission to stop the vigilante, but I think eventually he'll stop seeing Arrow as an adversary -- if only he know who was really behind the hood (he did arrest Oliver for being the vigilante, but was thrown off thanks to cleaver planning by Oliver and Diggle).
Tommy Merlyn (Played by Colin Donnell)
Tommy is Oliver's childhood friend and fellow party boy. In Oliver's absence, he began a relationship with Laurel Lance, which has cooled off since Oliver returned. Not much is know about Tommy yet, but I suspect he will either turn out to be a trusty sidekick or his greatest enemy.