'Arrow' Season 4 SPOILERS: Matt Ryan's Constantine Appearance Preview from Marc Guggenheim

One of the big selling points of the early part of Season 4 of Arrow is the news that Matt Ryan will appear as Constantine. In a new interview, executive producer Marc Guggenheim offers a detailed preview of the guest star's appearance. [SPOILERS to follow]

Guggenheim spoke to Superhero Hype and said that Ryan's appearance on the show feels like a full-blown crossover more than just a one-off appearance. Remember, NBC cancelled the show Constantine after just one season, but Arrow now provides a chance for the character to live on, however briefly that may be.

“When you see him in the show, honestly it feels like we’re doing a Constantine/Arrow crossover, and it’s so exciting," Guggenheim said. "We’re just really glad we got the chance to extend Matt Ryan’s run as Constantine by at least one more hour of television.

"I think you’ll see he fits very neatly into our universe," he continued. "It never feels forced, it feels right. Stephen [Amell]’s on screen vibe with Matt is just very natural, it’s as if these guys had been working together forever. I think people are really going to love the episode. John Badham (WarGames, Saturday Night Fever) directed it and it was just a happy circumstance, but John had also directed an episode of Constantine. It all works and it works really effortlessly. It worked effortlessly with a lot of effort I should say. I can’t wait for people to see that episode, if you thought it was a thrill just to see that one shot of Matt in the trailer wait til you see a whole episode with him.”

Stephen Amell had talked in the past about potential Constantine crossovers, and he even campaigned on social media to guest star on the series if Netflix, Hulu, or another outlet picked up the show after NBC canceled it. That never came to pass, but at least we'll get to see Ryan on Arrow.

We also know Constantine's appearance is tied to the resurrection of Sara Lance (Caity Lotz) as the White Canary.

What do you make of Guggenheim's remarks? Let us know in the comments section below.