At first the Kromaggs would seem to be historically wrong, since the Cro Magnon Man on which the sliders speculate they are descended from were the first "modern humans" - but that's on OUR Earth Prime. That means that the Sliders are actually further from our modern human species than the Kromaggs are! In short, WE are the Kromaggs (or at least are a close parallel)
For all the debate about which Arturo slid, the series left one clue that resides in this trope. In Season 3's "The Guardian," Arturo says he has just seen his first American football game, but in Season 1's "Summer of Love," Arturo knew the context of "wish-bone" and seemed very familiar with the sport in general. Both episodes were written by Tracy Tormé, who whenever asked about this, would reply along the lines with "Maybe you're on to something." In 2009, Tormé stopped implying and outright said that it was the alt-Arturo who ended up with the Sliders.
It's almost certainly unintentional, but the two Arturo's attitude to American football fits their respective characters well. Original "good" Arturo would be more likely to take an open-minded interest in the sport upon coming to America, whereas his nastier, more elitist double would probably disdain the American sport.
In "Paradise Lost" (which is a rip-off of Tremors), the mutated monster leaves behind a trail of blue slime wherever it goes. The locals don't try to kill it because its slime can prevent aging and prolong life. How is this Fridge Horror? The slime only works this way if you eat it.
In "Gillian of Spirits," Quinn is trapped on the astral plane and can only be seen and heard by the titular Gillian. She has a history of hearing voices and many (including Gillian herself) think she's crazy. And the voices did eventually go away. However, given Quinn's predicament, perhaps those voices weren't merely in Gillian's head. Perhaps they were other Sliders, who unlike Quinn, weren't as fortunate to escape the astral plane alive.
In "The Other Slide of Darkness," Maggie comments that she was never much of a team player. The sentiment is echoed in "This Slide of Paradise," where she says she didn't learn to be a team player until joining up with the Sliders. Of course, before joining up with the Sliders, she was in the military for years. Maybe not being a team player is the real reason why she went from fighter pilot to intelligence officer.
In "A Thousand Deaths," Rembrandt and Mallory take part in the Arcade, a place with sophisticated, realistic video games. Later, you learn the Arcade's big secret - the video game characters aren't mere holograms, but real people hooked up to the system. Everything done to them is real and after a thousand deaths in-game, they die for real. One game mentioned but not seen is a hospital game, where a player gets to be the doctor in emergency room surgery. On a world that seems to run on Video Game Cruelty Potential, think about that for a second.
In "Summer of Love," the Sliders barely escape an incoming swarm of the dreaded spider-wasps. However, right after Quinn and Arturo emerge from the vortex onto the next world, several spider-wasps are shown flying right out. So few probably wouldn't have the same effect as on the previous world, but they would still be enough to cause significant damage. More so if one happened to be "queen" potential!
It was never explained whether they reproduced like spiders or wasps. In either case, only three got through, one of which was crushed by Arturo. There's only a 50% chance they were the same gender; even if they were, and these things reproduce like spiders, they would have had to find each other again and not get killed in the meantime. AND, with such a small gene pool, it's quite possible some recessive gene will kill all of them - especially likely since they were genetically engineered rather crudely. However, if all those things go wrong, yeah, things are going to get very unpleasant in that universe shortly later.
In "Summer of Love," the American president is said to be Oliver North. The later "Exodus" two-parter also has Oliver North as president. While possible a coincidence, fans have suggested that both storylines featured the same parallel Earth. If true, then all those people the Sliders befriended in the former wound up dead in the latter.
The worlds seemed to have some other similarities. Maggie once mentioned that the Pacific War with Japan lasted longer in her world, as did the Cold War. While the specifics mentioned weren't the same, this corresponds to the world of "Summer of Love" which was stuck in the Cold War 60s.
In "The Weaker Sex", everything the Sliders were about to accomplish is undone by an ill-timed slide. But if you think about it, their intervention must have left things far, far worse than before.
This could not be more wrong. Think about this: Arturo's the first man to run for mayor, and there's a history of violence against him (e.g. people throwing bricks into his campaign offices). Just after he gets elected, he completely disappears off the face of the Earth. That he was murdered by someone who didn't want men to gain power would be a very logical conclusion, and that would make him a martyr, increasing support for the cause of gender equality.
Colin's fate, to be "unstuck," that is, bouncing around dimensions "for the rest of his life." Eesh...