A
problem that
plagues a lot of
TV shows, many of them of the
anime variety. Notable examples of the
phenomenon include many
X-Files and
Star Trek episodes, and basically all of
Dragonball Z.
Monster of the Week protocol:
Draw scary looking MONSTAR. MONSTAR does naughty things. Regular crew of the TV show fight said MONSTAR for 1 or more episodes. Characters eventually manage to kill it, or at least send him to the next dimension. Has no bearing whatsoever on the overall plot. Lather, rinse, repeat.
MotW episodes are filler. I really dislike them, although they do seem to provide a nice break between plot advancement-heavy episodes. Imagine if the X-Files was ~26 back-to-back Conspiracy Theory-style shows? All of our brains would explode.
*Oh yeah, if the show is anime, the MotW must have at least one super mega death ray of some sort. You know what I'm talking about.