These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Narm: Hoo boy. Probably most notable is the episode "The Great Vegetable Rebellion," where Mark Goddard has noted that during several shots you can see him deliberately not looking at the vegetable people so he wouldn't laugh.
Or better yet, ignore the movie and just buy the soundtrack (the Intrada score CD, not the song album - while the latter does have 30 minutes of Broughton, you have to sit through an awful lot of techno [in both senses of the term] to get to it. And most of the songs are only heard over the end credits anyway! Plus Broughton's stuff is all on the lengthy score CD under other names).
Inferred Holocaust: In the movie, since the Proteus had an entire sphere housing a botanical garden, it's possible it was one of many Space-Arks built to contain the last survivors of the human race; since without John Robinson to lead the team in building the Hypergate at Alpha Prime, Humanity would have been utterly screwed when the planet became uninhabitable.
And it's heavily implied that Blarp's vessel wasn't the first ship the Spiders stowed away on. Particularly since it's shown that they can survive in the vacuum of space and remain dormant for decades at a time and mutate other creatures into hosts to incubate their young...
Tear Jerker: The near loss of the Robot as he's swarmed by the spiders aboard the Proteus, sure he'd tried to kill the Robinsons earlier but that wasn't his fault.
Unfortunate Implications: In his Nostalgia Critic review, Doug Walker does not let it slide that John Robinson, saying what could be his last words to his spouse, refers to her "as the role of 'wife'" rather than by her name.
What an Idiot: In the movie, John discovered Future-Will had built a working time machine with enough power for a single one-way trip. When he sees his ship along with his family perish in a meteor shower in the atmosphere of the planet, he decides to use the time machine to travel back a few minutes and prevent their deaths. Sounds all well and good, if you don't take into consideration he could've just gone back to the day of the shuttle launch that sent him and his family spiralling through time and space to unknown reaches of the galaxy and prevent the entire plot of the movie.
Actually this is explained in the film itself. The gravity and temporal anomalies generated by the device are literally ripping the planet apart, so connecting the time-machine to anywhere near Earth would not be a good thing!
And Heather Graham as Judy Robinson! I repeat - HEATHER GRAHAM as a scientist's daughter!!
A lot of criticism was sent William Hurt's way, who was anchoring a summer effects-laden sci-fi popcorn film and his approach was virtually the same as his very dramatic roles, which didn't help when he needed to deliver wooden dialogue such as "I love you, wife".