Shill

A shill, also called a plant or a stooge, is a person who publicly helps or lends credibility to a person or organization without disclosing that they have a close relationship with that person or organization or have been paid to do so, often posing as an enthusiastic independent customer to influence onlookers through crowd psychology. Shilling is illegal in many jurisdictions because of its potential for fraud and financial harm, though it is not universally prohibited; the practice can be lawful where it does not place uninformed parties at financial risk, as with paid audience participants used for effect in a stage performance. The legal line generally turns on whether vulnerable people are exposed to genuine financial harm or deception, rather than on the act of paid endorsement by itself. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/