The other four moons in the system — Styx, Nix ... Pluto and Charon are tidally locked to each other, meaning they always show the same face to each other, and they orbit their common center ...
This slow collision would have caused a "geologic reset" for Pluto, as Charon stripped some of its ice, and potentially led to the formation of Pluto's smaller moons — Nix, Styx, Kerberos ...