In a typical Star Trek episode you have the regular cast (i.e. the ones listed in the intro), possibly some recurring characters (e.g. Garak or Lwaxana Troi), and usually also at least 1 main guest actor/actress who has a significant role in the plot.
There's typically also non-speaking background extras and some random non-speaking dude at the helm, but I'm not counting those.
So I'm curious: are there any Star Trek episodes from any series that feature no speaking guest cast, but only regular, recurring and background cast?
The (widely loved) TNG clip show 'Shades of gray' fits the description for the newly filmed parts (only the main cast and the universe's favorite recurring transporter chief Miles O'Brien), but the flashbacks do contain other guest actors.
I've looked at the list of bottle shows, but can't find any there.