To be honest, Arthur has been re-treading plots for a while now - I recall the "persona swap" being a device used often ("Popular Girls", "Buster's Best Behavior", and to a degree "It's a No Brainer"). One could argue most plot points/devices were used up as early as the 3rd season, though that's out to debate. I suppose when you run a fairly straightforward (and somewhat restricted) show for almost 20 years, these things happen.

Hasn't there been TWO episodes now that featured a plot in which D.W. had trouble getting rid of hiccups? I know it was a subplot in "Arthur Vs. the Piano", but it seems like one of the more recent seasons used it as the A-story of an episode.