  Extreme Scattering Events (ESEs) are dramatic variations of the flux density
at Gigahertz frequencies caused by ray path distortions within an isolated
inhomogeneity ("plasma lens") in the interstellar medium. These events are
characterized by a deep flux density minimum in the light curve with, in some
cases, surrounding maxima. The variability time scales range from weeks to
months. These phenomena show a strong frequency dependence, in which the
variability amplitudes increase with wavelength. During an Intraday Variability
(IDV) monitoring project (March 2000), a feature resembling an ESE-like event
appeared in the variable light curve of 0954+658, however with a time scale of
less than two days. We will discuss this effect and its implications for a
better description of the interstellar medium.
