"Invasive Procedures" is what's referred to as a 'bottle show'. Designed to save money over the course of a TV season, the episode uses a small guest cast, no extras, and utilises only standing sets with no location shooting. Given the fairly significant production costs of the season's first three episodes, it's unsurprising that some costs were cut while making the following week's adventure.
This is by no means a bad episode, but it's by no means an exceptional one either. It's very much a middle of the road Star Trek episode, pleasing to the converted and probably fairly dull for those not already on the Trek wagon train. Specific observations are, like always, covered in dot point form.
- The episode is centred around a guest performance by John Glover, who's always been a fairly engaging and idiosyncratic performer. He's great here, particularly when - for plot purposes - his personality changes quite significantly halfway through.
- It's nice to get some more background and insight into the Trill species, in which a centuries-old hyper-intelligent slug lives inside the abdomen of a human-like host. It's a neat idea and it's played out very well here.
- Tim Russ, who will later play the Vulcan security chief Tuvok in Star Trek: Voyager, plays a Klingon here, and to be honest not too well.
- Overall the episode is a little ordinary. It doesn't engage as much as the episodes before it, and it doesn't engage as much as the one after it ("Cardassians"). It's simply rather average.