But we're not talking about recurring roles here, are we? We're talking about a practice in TOS and other series from that era, in which recurring guest characters were uncommon. Actors who played multiple roles generally played them one time each. And since episodic TV was pretty formulaic back then, often a lot of those one-shot characters would be pretty much the same -- the love interest, the villain, the cop, the opposing lawyer, that sort of thing. So if you got a script that had another character of a certain type, you might naturally gravitate toward a certain actor that you knew was suited to that type and that you'd used before. Aside from Combs playing Brunt and Weyoun, I can't really think of an instance in live action where one actor has played more than one recurring character on an overlapping basis on a single series. Well, except on Hercules/Xena -- Karl Urban played both Caesar and Cupid, Kevin Smith played both Ares and Iphicles, Lucy Lawless returned as Lyla after having played Xena, probably a few others. But those shows were kind of weird.