When some actors portray a villainous role, they take a somewhat “method” approach, which can involve living in character for months at a time and, in some instances, even terrorising their co-stars all in the name of getting in touch with their dark side.
Article source: https://www.huffingtonpost.co.uk/entry/emma-thompson-admits-she-was-told-off-by-matilda-director-matthew-warchus_uk_639459b2e4b0169d76d75cb4