Toady's cinema is full of films using digital effects to sell their particular fantasy.
Green or blue screen is the most common, were large areas of the frame are adorned with large areas of Chroma green or Chroma blue material. This Chroma colour material is specially designed with colour saturation at a particular wavelength which enables the post production software to easily select it and effectively make it disappear through 'Matting'. The next stage is to add the 'made up ' fantasy element in the now empty areas of the frame. This can either another feature a real video shot separately, or more likely to be a computer generated CGI image where the digital artists potentially have no limits and their imagination can run wild.
Below is Greenscreen example from 300 Rise of an Empire
Below is a clip from Tim Burton's Alice in Wonderland, this include the added complexity of moving elements. the characters wearing green have 'coins' or markers on them to assist the Effects house substitute the real movement for that of the CGI version as seen in the next picture below