Awesome Music: John Williams' theme song from season three. He also scored four season one episodes ("The Reluctant Stowaway", "Island in the Sky", "The Hungry Sea" and "My Friend, Mr. Nobody").
Ensemble Dark Horse: Dr. Smith and the Robot were by far the most popular characters, with Jonathan Harris himself calling them the whole reason anyone watched the show. Funnily enough, neither was in the original pilot and we have an extensive Retool before the main production to thank for their existence.
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. The episode's writer openly admitted he was completely out of ideas after three years.
They Copied It, So It Sucks!: The concept is identical to the Space Family Robinson comic that debuted three years earlier. Rather than sue, Gold Key Comics settled out of court with the deal that they could use the Lost In Space title in the comic.
John will occasionally invoke the Stay in the Kitchen trope to Maureen whenever she tries to be helpful in a dire situation.
Likewise, Will frequently underestimates his older sisters' intelligence simply because they're girls. And because they're girls, he will almost always prefer to be in the company of Doctor Smith, despite him being clearly less competent and more cowardly than Judy and Penny.
Awesome Music: Bruce Broughton's score, especially when the Jupiter 2 flies through the collapsing planet. Both the original, rejected theme and the in-film version are fantastic. 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). Although you gotta admit that Apollo 440's take on the John Williams' famous theme song was pretty good.
Best Known for the Fanservice: Heather Graham and Mimi Rogers in form-fitting rubber suits. Though it's killed a bit by 14 year old Lacey Chabert also getting one.
Complete Monster: Dr. Zachary Smith was already a self-serving sociopath throughout this film, however it isn't until later, through the means of time travel, that we see his truly monstrous future self. Originally working with the international terrorist group known as the Global Sedition, Smith tried to murder the entire Robinson family, including the children, just to make a quick buck. However, when the botched assassination ended with him stranded on an alien planet with the family, Smith showed himself to be an absolutely depraved monster. Having mutated into a monstrous spider-like creature, Smith murdered and possibly ate the defenseless Maureen, Judy, and Penny Robinson, then manipulated young Will into building a time machine in order to save his family from death, all the while making Will see him as a father figure. When Smith meets his past self, he mocks him for lacking "true ambition" before attempting to murder him. After Will completes the time machine nearly two decades later, Smith tries to kill him while revealing his master plan to use the machine to travel to Earth, then unleash a horde of spider monsters to ravage the planet and rule over them as a god. In a sharp contrast from his original humorous and clumsy iteration, Dr. Smith is a truly wicked individual who cares for nothing but himself.
Ham and Cheese: Gary Oldman as Dr. Smith. And he seems to get increasingly hammy over the course of the film. Initially, he starts out somewhat restrained, but once he's trapped in space with the Robinsons it's like he's given up all attempts to be subtle. He openly admits to being a monster and evil at every given opportunity with what could only be described as sheer glee. His antics on the Proteus in particular are on par with a Saturday morning cartoon villain. Then there's Spider-Smith...
Penny-vision brings to mind many YouTube vlogs and selfies.
The TV series took place in 1998. The movie was made in that year.
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. However, things may not have been so hopeless. Jeb's video log references a "hyperspace tracker" implying that the Proteus was in fact looking for the Jupiter 2, and given that they appeared around the planet the Jupiter 2 arrived at implies that in the intervening years between the Robinsons going missing and the Proteus being created mankind has developed more advanced means of navigating hyperspace to the point they can track the flight path of lost ships through it. Ultimately making hypergates useless. 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...
Moral Event Horizon: If Smith hadn't crossed it when he tried to sabotage the Robinson's trip by programming Robot to kill them all, children included, he surely crossed it in the timeline where, once he mutated into a spider-like monster, murdered them all himself, except for Will whom he manipulated into building a time-machine so he could go back in time and take over the world with his army of spiders.
Blarp the CGI spider monkey. Looks less convincing than an equally cheap-looking puppet, and assuredly was more expensive.
Dr. Smith's alien-spider form is a treasure trove of badness. It's badly composited into the practical-effects cloak he starts with—his head rapidly wobbles in his hood. The actual design is almost impressive, except for the hugely long neck that makes no sense given he was mutated by Cephalothorax space spiders. In action, it lacks weight and doesn't quite line up with the set or actors.
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.
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. The movie attempts to justify this by having John worry that Will's time machine might destroy Earth, as it was destroying the planet it was built on, but that conclusion was a guess at best, and as a matter of fact Will had already connected to Earth before changing the coordinates.
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".