We know from the Tenth Doctor story "Fear Her" that Star Trek exists in the Whoniverse. And we know from "The Gunfighters" that "Spectre of the Gun" would have been written differently. The loose thread would have to be different, for one thing; in the Whoniverse Ike Clanton died. And the script would call for more people beaming down. Which of the bridge crew would be best cast as Johnny Ringo, Phineas Clanton, and Pa Clanton?