This is discussion archived from a time before the current discussion method was installed.
Working Title: Acting For Twenty: From YKTTW
: Okay, the Star Trek
example is already over in You Look Familiar
...and that's probably the demarcation line. J.G. Hertzler playing five different characters in five different episodes is YLF. Brent Spiner playing Data, Lore, and Dr. Soong in one episode is this trope.