This is such a cute and funny video. My favorite part is the contextual explanation for the origins of the theatrical expression ‘catching flies.’ During the Vaudeville theater era, this expression was used to describe the action of one actor making faces, without being seen by the audience, in an attempt to distract and trip up the other actors on stage while these were delivering a monologue or engaged in a dialogue.
This activity is still common among certain students. I will have to remember to use it if I ever I catch one of my students doing so.
N.B. One should be careful to specify the theatrical sense of the expression to avoid that his or her students confused it with the non-theatrical contemporary meanings of the expression.