"Don't get me wrong, I love the voice acting in this game. But occasionally we have Chris Metzen congratulating Chris Metzen for slaying Chris Metzen."
Professional voice actors pride themselves on range. So, hiring a few good voice actors means you can take care of many, many characters
with a small cast (especially if one or two actors are a Man of a Thousand Voices
Oftentimes, this results in funny situations, like two characters played by the same person having intense conversations and heated arguments with each other. The talent is in making sure the audience doesn't know it.
If jokes are made about this, it's Actor Allusion
In voice acting, the process is fairly simple, with the actor just doing a different take (although some good voice actors can do it in real-time). The actor's vocal range is the only thing that might betray commonality.
This is sometimes actually invoked on purpose
, as it can make you think, "Ohey, they're a clone? Why didn't I realize that before?"
In Live-Action this can be difficult, which requires split screen or otherwise splitting the image. This requires perfect synchronization between the different takes. Normally, the camera is stationary for this, but Back to the Future Part II
pioneered a motion controlled camera that allows for complex panning shots that have the same actor in multiple roles.
Not to be confused with I Can't Use These Things Together
, Sounding It Out
, Thinking Out Loud
or Talking to Themself
. Compare Holding Both Sides of the Conversation
, which is an in-universe example of this trope, where a character is pretending to hold a conversation with another non-present (or non-existent) character, in order to maintain some kind of charade.