Who played John Keating in 'Dead Poets Society'?

In which film is Sean Maguire a character? Who played Jason Bourne in 'The Bourne Identity'? Who played Mark Watney in 'The Martian'? In which film is Mark Watney a character? In which film is John Keating a character? Who played Adrian Cronauer in 'Good Morning, Vietnam'? Who played Agent J in 'Men in Black'? In which film is Agent K a character?