Cha chas tend to wear open-toed shoes, flip-flops, and chancletas.
"Look at that cha cha over there. That fatty shouldn't be wearing a tank-top!"
In this case the person did something to upset the applecart or cha-cha of someone else.
I have also heard, Go along with the cha-cha. Here it is like the word "program" as in go along with the program, or cha- cha.