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.
Actor Allusion: Possibly unintentional, but "Into the Mystic" has the gang crossing a high bridge above running water that looks awfully familiar.
Angst? What Angst?: For someone he regarded as a father figure and close friend, Quinn didn't seem to grieve all that much over Arturo's death. A flash of anger in "The Other Slide of Darkness" is all we get. For that matter, Quinn didn't seem particularly concerned that Wade (his best friend) and his own mother were in the clutches of the Kromaggs.
Arturo: I am not Mr. Pavarotti! Mr. Pavarotti is an Italian! He speak-a like-a this! Do I speak-a like-a this?! No! Why?! BECAUSE I AM AN ENGLISHMAN, YOU BLISTERING IDIOT!!
Made even more funnny if one considers John-Rhys Davies is actually Welsh in real life.
Ensemble Darkhorse: Logan St. Clair, a once-off villain who was meant to be a recurrer but never re-appeared due to Executive Meddling, but whose wild popularity with the fans led to her being included in seemingly half of the Sliders Fan Fics ever written.
You mean the evil, sexy, female version of Quinn? Of course she's uber-popular!
Conrad Bennish, Jr. is amazingly popular with the fanbase. He only appeared in four episodes thanks to Executive Meddling, but he was an instant fan favorite. He probably appears in more fanfics than even Logan.
Ethnic Scrappy: Rembrandt veered dangerously close to this at first; he eventually got better.
Executive Meddling: And how! Creator Tracy Tormé was booted in favour of David Peckinpah after Series 3, who steered the show to plots that rehashed popular movies. Likewise, Jerry O'Connell gained increasing amount of control after becoming a producer, writing, directing and adding his brother to the cast. Whether these changes were welcomed by fans... lets just say it's a touchy subject amongst fans and leave it there.
Fanon: Because of her last name and her father being a military man named Tom, some fans are convinced that Maggie had an uncle who was a double of a guy named Sam.
Fanon Discontinuity: Reviewers at IMDB are unanimous. Watch the first two seasons and then quit while you're ahead. You have been warned.
Franchise Original Sin: The Season 2 episode "Invasion", which introduced the Kromaggs. Many fans frequently praise the episode, but then the Kromaggs became the sole focus of the series starting in Season 4 (after a season-long absence, no less). Much of what made them interesting was also discarded. Note that Tracy Tormé (writer of "Invasion") said at the time that he was against overusing the Kromaggs out of fear of what ultimately happened.
"Funny Aneurysm" Moment: The episode "Season's Greedings" had lots of Christmas ads that were very commercialized. Nowadays they seem normal.
Hell, even at the time, fans made jokes about how the Sliders must be home if they'd landed on a world where Christmas was overly commercialized.
Genius Bonus: The For Want of a Nail element is often implied, rather than stated outright, or is assumed but turns out to be wrong. For instance, the pilot assumes that the difference is that the US lost the Korean War, triggering the Domino Effect, but a passing remark implies that the Soviet Union and China united to become The Empire, rather than viewed each other as enemies as in the real world.
Hilarious in Hindsight: Near the end of Season 4, "My Brother's Keeper" features a clone of Quinn, with a lot of talk how he is and isn't actually Quinn. The clone is only designated as Mallory, leading to Rembrand to question, "They couldn't even give him a first name?" Keep that in mind a few episodes later when Season 5 starts.
The entirely of Season Five was a pain to watch. Especially getting rid of Jerry O'Connell in one of the lamest excuses for a recast, and de facto killing one of the most beloved characters of the show. All within one Slide. It goes downhill from there.
Tear Jerker: In "Applied Physics," Mallory struggles with Quinn's memories and 'remembers' Arturo:
"I don't know who he was, but he meant so much to me I can't stop hurting."
The end of "Gillian of the Spirits," when it looks like the others will have to leave Quinn behind.
The second part of the pilot had the gang travel to a universe where San Francisco (and possibly all of Earth) was in the grips of a new ice age. Quinn finds a photo of his "family" in a drawer, but with the addition of a dog and his would-be sister. While the sister thing is sad, it's this comment from Quinn about the dog that always gets me:
"That's Bopper. But he ran away when he was just a puppy. We never found him."
Villain Decay: The Kromaggs. Season 2's "Invasion" showed them to be quite threatening, as well as calculating and simply quite unpleasant to look at. When they came back for Season 4, however, the make-up was less elaborate, and they were overall more generic bad guys. Some of the mental tricks and careful planning remained, but things could also get hammy depending on the episode. Fans also objected to the heavy-handed Nazi allegory the writers started using.
They Wasted a Perfectly Good Character: Logan St. Clair, as evidenced by her frequent use in fanfics. She put a new spin on doubles for the series, could match Quinn in the brains department and be far more ruthless.
They Wasted a Perfectly Good Plot: "The Exodus" two-parter. Consider: a doomed world, the Sliders racing to save everyone they can, finding Earth Prime, the death of Arturo, the addition of a new Slider (one who's not shy about causing inter-group conflict) and the emergence of a new Big Bad. On paper, these sound like some pretty interesting (if not epic) ideas that would provide a wealth of storytelling potential. But the execution? Well, Tracy Tormé and many others consider them some of the worst episodes the series ever produced - if not the definitive examples.
The entire premise of the series itself, wasted by the execution, if you consider even the early episodes as disappointing.