There have been several times in the various Star Trek series when one actor interacted with himself/herself as a clone, Mirror Universe double, or other "alternate" version of the same basic character. But has the same actor ever played two completely distinct characters in the same scene?
For example, Jeffrey Combs once said that he always wanted to do this with Brunt and Weyoun, but he never had the chance to. And in the Deep Space Nine episode "Chimera," the alien guest star was played by J. G. Hertzler, and Martok is mentioned several times in the episode, but he never appears on screen.
Has it ever been done?