What do the Chinese call kwai-tsze or quick little fellows?

The term "kwai-tsze" is not a common Chinese word. It's likely a romanization of a Cantonese phrase, but it's difficult to know for sure without more context.

To give you a better answer, I need more information:

* What is the context of this term? Where did you hear it? What is it being used to describe?

* Are you sure the spelling is correct?

* Are you asking for a direct translation or a Chinese equivalent?

Once I have more information, I can try to give you a more accurate response.