Arrow fans were in for a special treat when series star Stephen Amell pressed play on the previously released preview trailer from the action-packed series' upcoming third season, featuring footage of Colton Haynes in the Arsenal costume, Brandon Routh as Ray Palmer and Karl Yune as Maseo. But Amell also had a Saturday night surprise up his sleeve - a new ending to the trailer which revealed that a nightmare is coming: Ra's al Ghul! Arrow returns Wednesday, October 8, at 8/7c on The CW. Take a look at the extended trailer below, then read on for more information from executive producers Marc Guggenheim and Andrew Kreisberg.

The trailer debuted during Warner Bros. and DC Entertainment's massive three-hour panel, which was hosted by Stephen Amell. After the panel, executive producer Marc Guggenheim revealed that Ra's al Ghul's introduction had been in the works for quite some time.

"It really happened very organically in the sense that we had this notion that in episode 16 we were going to reveal that Malcolm Merlyn was trained by the League of Assassins and that's because that's because of the comic book. We were like, you know what we're going to do? We're going to get away with a little reference about a guy in Nanda Parbat who changed his life. That was just the beginning."

However, he also revealed that they started to drop Easter Eggs in the third Arrow Season 2 episode, "Broken Dolls".

"We just slowly started creeping towards it and creeping towards it. Then discussions started happening with DC and then Superman-Batman started happening getting into clearer focus. The character seemed to be available as far as not being used in the movies. It was a very, very organic progression. That was what was fun for us, just how natural it happened."

The executive producer added that their version of Ra's al Ghul will be much different than Liam Neeson's portrayal of the villain in Christopher Nolan's Batman Begins.

RELATED: Arrow Season 4 Finale Trailer Reveals Darhk's Diabolical Plan
"We have a really clever way of doing Ra's this year that is true to the comic-book origins but different from the way Ra's was portrayed in the Nolan movies. You don't want to compete with Batman Begins, even though we've always said Batman Begins was a big influence on us. We really wanted our Ra's to be very different - at least our own Arrow-ified version."

He added that they didn't want to "over-milk" the Ra's reveal during the second season.

"When we were talking about Ra's in the third episode in season two, it was [a question of] how many times should we mention his name? How often should we talk about him? Because he has a lot of power especially on the comic-book side. We didn't want to over-milk it and overuse it. We not only show you a little hint of Ra's, we also repeat all the times we mention his name, which shows you how long we've been talking about this and thinking about this."

Executive producer Andrew Kreisberg teased that there could be a chance that Oliver (Stephen Amell) and Merlyn (John Barrowman) team up, now that Ra's is in play.

"We've established firmly that Ra's al Ghul hates Merlyn and Oliver doesn't like Merlyn. It's going to be series of who hates who more. The enemy of my enemy is my friend."

The producers are currently casting Ra's, who will appear early on in Arrow Season 3, although they would not confirm exactly when. Of course, Ra's is the father of Nyssa al Ghul, who was played by Katrina Law in Season 2. Marc Guggenheim revealed that the first time fans will see Ra's is during a scene with Nyssa.

"(Nyssa) will absolutely play into the season and we have a really cool arc planned. The first time we see Ra's is a scene between him and Nyssa."

In related news, another new hero will debut this season, Wildcat, who hasn't been cast yet. It is said that Wildcat will have an encounter with Laurel Lance (Katie Cassidy).

Are you more excited for Season 3 after these new revelations? Chime in with your thoughts below.