Maggie Smith (Minerva McGonagall)
The actress was already such a prominent figure in the British culture and art scene that Queen Elizabeth II made her a Dame in 1990. She was cast as the Head of Gryffindor and Head of Transfiguration, Minerva McGonagall in 2001 and appeared in seven of the eight films in the series. Unsurprisingly, Smith had plenty of roles after the Potter series ended, including Violet Crawley, Dowager Countess of Grantham in the TV series Downton Abbey for which she received a Golden Globe Award and two Emmy Awards.