Big Charlie is a particularly strange one of Trevor Henderson's creations, partly because not much is known about it. He is also SCP-4158 by the SCP Foundation. Big Charlie is a large mammal-like creature, it resembles some sort of cattle, yet, at the same time, it has a beak-like protrusion on the tip of its mouth. Its body is so skinny that that you can see its ribcage. It also has a thick dark mane that goes from its head to the back of the creature. Its eyes appear to be foggy, which might indicate that the creature is blind, though in most depictions he does have normal eyes. Its legs are very lengthy compared to its body and it seems as if its legs can barely support its weight. Big Charlie is around 20-30 feet tall. According to Trevor Henderson's Tumblr post, it is said that he escaped a meat-processing plant. Meaning he is some sort of animal made out of meat possibly.
Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing.