The term 'Animation Unit' refers to a group of people who work together to create animated films and television shows. The crossword solutions for this term include the word 'CEL', which is an abbreviation for celluloid, a type of transparent sheet used in traditional animation. Cels are painted on one side and placed over a background image to create the illusion of movement. This technique was used extensively in the early days of animation and is still used today in some forms.