My favorite example of this was during a lecture on waveguides, when Michael Schick picked up the section of cylindrical metal pipe he was using to motivate the

My favorite example of this was during a lecture on waveguides, when Michael Schick picked up the section of cylindrical metal pipe he was using to motivate the cylindrical-waveguide problem at hand, looked at the class through the pipe, and said, "clearly, it admits higher-order modes." That little episode brought great joy to this experimentalist's heart.