Fred:

In logic studies they call those things self-referential loops. The definitive study on them is part of Godel, Escher, Bach, a weighty intellectual tome from the 70's that I even waded through one time. THe classic examples are things like "This sentence is not true." And the piece of paper that keeps Republicans occupied forever because it says "Answer on other side" on both sides. :>)

Th showmanship items are sometimes called "bits", "gimmicks" or "pieces of business" in thespian circles.

A