"Murder on the Planet Express" gives us one of the few episodes about paranoia that actually make the viewer feel paranoid. Whether that's good or bad is up to the viewer. I thought it was good. Or did I?
Most movies or shows about paranoia and a culture of mistrust fail to impart the feeling to the viewer because they're mainly thrillers, dramas, or Art That Makes a Point. We know the rules of all of these genres, and so they can't fill us with uncertainty. In comedy — especially screwball comedy — anything can happen, which can leave the viewer far more off-balance than more serious genres.
We see this clearly in "Murder on the Planet Express," when the Planet Express crew develops trust issues. Each employee suspects another of some minor crime, and it gets bad enough that the Professor forces them all to go on a corporate team-building retreat to work on their trust issues. When the leader of the retreat tells them to pick up a hitchhiker, and the hitchhiker turns out to be a murderous shape-shifting monster, the team has to choose who to trust. Anyone reading this can see the escape hatch in the plot, but even if there weren't one, it's a science fiction comedy show — deus ex machinas are easy to come by.
Oddly enough, this makes each scene more tense. Since we know no real harm will come to the characters, anyone could get eaten at any time in any scene. It also makes all the comedic stings more funny. They're a bit like the old Warner Brothers cartoons — giving us a set-up that lets us expect one thing and then veering off in a different direction. If there's one problem, it's that the show keeps the uncertainty coming too long. The trouble with The Lady or the Tiger endings is that by their very nature they leave the audience unsatisfied, so the weak element of the episode is built into the plot. The core of the episode, with the monster eating random members of the crew, is glorious, though. (And did anyone else catch the Wernstrom Reverse Scuba Suit cameo?)