In the olden days, if footage was not used in a film, it was either destroyed or erased so they could reuse the reel, because it was cheaper than storing unused film.
Google the BBCβs lost archives to find out more.
One artist draws something, and then makes it a silhouette, gives this to another artist who doesnβt know what the actual drawing is, and they have to make a drawing within the silhouette based on what they think it isΒ