Mercury/Pluto combines Mercury's association with speech, thought, communication, and perception, with Pluto's associate with the depths, the instincts, the taboo, the mysterious and hidden:
The Mercury/Pluto combination is often associated with speech and the mouth (Mercury) combined with the taboo and libidinal impulses associated with Pluto. One of the ways Mercury/Pluto in the chart of Miley Cyrus shows up is in the singers tendency to stick out her tongue: https://www.youtube.com/watch?v=5tFcHZtrLRU
The tendency of the Mercury/Pluto combination to involve taboos and power (Pluto) in the realm of speech (Mercury) in the chart of Madonna shows up in this interview with David Letterman in which she uses profanities (Mercury/Pluto) and engages in power struggles (Pluto) of communication (Mercury) with Letterman involving sexuality (Pluto): https://www.youtube.com/watch?v=PBm5kzTYfNU
The Mercury/Pluto combination in the chart of Keanu Reeves shows up in his role as Neo in the movie The Matrix, who is able to perceive (Mercury) at such a depth (Pluto) that he discovers what he thought was reality is really an program.