- Actor Allusion: An interesting variation - in the original novel, prot lists Starman as one of his favorite films. Starman was about a benevolent alien visitor played by Jeff Bridges. The novel, which is written in the first person by Dr. Gene Brewer as a psychological case study of prot, mentions that it's been optioned into a movie towards the end, so it's entirely possible that we're watching the same film the book's characters eventually see, Jeff Bridges and all.
- Adaptation Displacement: The novels' existence comes as a surprise to many. The film is actually a rather faithful adaptation of Dr. Gene Brewer's 1990 novel, which itself has three sequels.
- Fridge Logic: Having a reproduction method that is painful and disgusting would make a species very likely to have died out long ago, rather than allowing them population control from rare use of it.
- Debatable, considering that there's plenty of non-human animals on earth who have painful, or even fatal, copulation and childbirth methods and it hasn't threatened their populations.
- Mary Suetopia: The description of prot's homeworld is basically a perfect anarchist, agnostic society with no violence, everyone is vegetarian, and there are no schools. Criminals are not punished; they are simply "reasoned" with (or they would be reasoned with if there were any there in the first place).
- Jerkass Woobie: Some of the patients are generally unpleasant people, but they are suffering from mental disorders which may or may not be the reason they act that way. Sal is the best example-he's surly, rude, and tells people they stink. However, he used to be a normal man working as a doorman at a hotel for years, when suddenly one day he began to think people stank. In the book it's a bit played for laughs. In the film, Sal telling prot "I tried to tell them, but they put me here, and...this place smells worst of all" is a Tear Jerker with the delivery of the line. He then tells prot that prot doesn't smell, which is why he's hoping prot can help him.
- The Woobie: Good god, Robert. Father dies from a work injury at an early age, girlfriend gets pregnant and to support her you have to take a dead-end job in the same place your father worked (possibly even the same job, it isn't specified), and then one day you come home from work to find your wife and daughter raped and murdered in your home. Little wonder he was Driven to Suicide.
- The book makes a good deal of the patients this. The reason Howie is obsessive compulsive is because his father was demanding and never tolerated mistakes, and Howie loved him so much he was determined to learn everything so he could please him. Ernie meanwhile had a father who would run emergency alarms in the middle of the night, shouting for the family to wake and run out of the house. The book mentions that Ernie's current state is a big improvement from when they first got him, where he would jump every time someone sneezed.