In the clip, director Lucy Forbes explains that the team went through "many, many different phases" of designs for the character, while creator Abi Morgan says that there was a "huge legacy of monsters" that they had to "steer away from".
Cumberbatch then explains that Eric was inhabited by "a truly gifted performer", Olly Taylor, the lead puppeteer on the series, while his voice was put over the top afterwards.
You can watch the full clip right here now.
In the clip, it is revealed that Taylor had no vision out of the Eric suit, so instead he wore goggles which displayed to him screens, and cameras were dotted around the location so he could see what was going on.
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Cumberbatch previously told RadioTimes.com that voicing Eric was "a joy" and that it was "one of the biggest draws to doing the character, to doing the role, to being part of this drama".
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However, he also admitted that fills him "with fear" as he doesn't "know how people are going to respond to it".
The series follows Cumberbatch's Vincent as his mental health deteriorates following the disappearance of his son Edgar. Together with a manifestation of his son's puppet monster Eric, Vincent tries desperately to get Edgar back.
Eric is available to stream on Netflix now. Sign up for Netflix from £4.99 a month. Netflix is also available on Sky Glass and Virgin Media Stream.
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