the brave little toaster to the rescue plow scene

This requires perfect synchronization between the different takes.

In Live-Action this can be difficult, which requires split screen or otherwise splitting the image.

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?' The actor's vocal range is the only thing that might betray commonality. 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). If jokes are made about this, it's Actor Allusion. The talent is in making sure the audience doesn't know it. Oftentimes, this results in funny situations, like two characters played by the same person having intense conversations and heated arguments with each other. So, hiring a few good VAs means that 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). Professional voice actors pride themselves on range.

The brave little toaster to the rescue plow scene