Keanu Reeves played Bart Simpson in Johnny Mnemonic.
Johnny Mnemonic (film) . Keanu Reeves plays the title character , a man with a cybernetic brain implant designed to store information . Keanu Reeves . A recurring character arc in many roles he has portrayed is one of saving the world , as can be seen in the characters of Ted Logan , Buddha , Neo , Johnny Mnemonic , John Constantine , and Klaatu .