Not being familiar with the type of thing you're asking about, nor how explicit a description you need of such an exercise, I'll go out on a limb with this.

A and B are students.  A is provided with the first sentence in each exchange.  A and B switch roles at some point.  The underlined words should be the same in all cases.

A.  My sister dropped the towel.
B.  Sorry.  I didn't hear all of that.  What did you say about the towel?
A. The towel was dropped by my sister.

All you need to do now is come up with tons of starter sentences. 

The obvious reverse pattern is to place the last sentence first, have Student B say, "Sorry.  I didn't hear all of that.  What did ..... do?", and the first sentence last.  I'm sure you get the idea.

Is that the sort of thing you're looking for?

CJ