impostor

Someone who pretends to be another person to trick people.

impostor in a sentence

The guard realised the man in the crown was an impostor when the real king walked in.
The new goalkeeper was an impostor who had borrowed his brother's kit and name.

fraud, fake, cheat

impudent: Rude and cheeky, showing no respect.
indulge: To let yourself or someone else enjoy a treat.
innocuous: Harmless, and not likely to upset or hurt anyone.
insolent: Rude in a bold, cheeky way.
interfere: To get involved in something that is not your business, often making it worse.
intervene: To step in to stop trouble or help sort something out.
justice: The fair treatment of people, where right is rewarded and wrong is punished.
juvenile: To do with young people, or behaving in a childish way.

Plain-English guides to each test, from the councils’ own pages: Kent Test · Medway Test · Bucks Secondary Transfer Test