Some of the key special effects scenes on NBC's Constantine may just comprise mere minutes of screen time, but behind the scenes, weeks of work have actually gone into creating the mind-blowing moments that make you jump.

Despite this fact, though, visual effects supervisor Kevin Blank says bringing the creepy world of Constantine is mostly scary fun.

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Blank, who previously worked on NBC's Crossbones, collaborates with Sweden-based visual effects studio Important Looking Pirates (ILP) to create the creatures on the comic book-based TV show and the world in which they play. "The work on Constantine is very VFX-intensive, and attractive in terms of ... how fun the things are and how outlandish the things are," he told Mashable.

Los Angeles-based Blank is a foreman of sorts; he guides the final product, which can present a number of challenges, especially when scenes involve a lot of moving parts, and time is of the essence.

The special-effects team usually has six to eight weeks to complete work on an episode — up from the usual range of three to six, which is partly due to Constantine's October premiere; it started production on the season in July. Although the extra time is appreciated, creating the sometimes seemingly short scenes involves multiple steps and departments.

Image: NBC

One particular scene that Blank is proud of aired in last week's episode, "Feast of Friends." It involved demon bugs.

Behind the scenes, as with anything in visual effects, the artists started with an inspiration: the Khapra beetle. "Then we said, 'Well, ours could be creepier.' So they changed little things," Blank said.

Building the assets — in this case, bug models — happens well before footage from the episode begins. Once that comes in, so-called rigging (which is necessary for the model to move), animation and other fine-tuning follows. In all, the bug work took about 12 weeks to complete, from script to delivery.

"If we can have our assets built in time, before the plates or the photography shows up, we're ahead of the game," Blank said.

Image: NBC

Keep in mind: It's not just demonic creepy-crawlies and big baddies that the team tackles. It can also be less noticeable details, like changing the look of a sky to better reflect the show's tone. Such things might seem like small details, but they're just as important as anything else, according to Blank, especially on Constantine, which incorporates the comics' aesthetic into the show.

"It's not uncommon for cinematographers to use paintings as reference for lighting, and I would say we are probably doing the same for comics in terms of details that we're looking to infuse into the project," he said.

It's a lot of work, but Blank says the effort is worth it. "Sometimes the schedule and the time and budget limitations seem to limit our fun, but we still are having a good time doing it," he said.

Check out more behind-the-scenes action from Constantine in the exclusive video, below: