- Played by: Jerry O'Connell
- Affectionate Nickname: Rembrandt calls him "Q-Ball."
- Basement-Dweller: He still lived with his mother while finishing college. He still had his own room, but converted his basement into a makeshift laboratory and spent most of his free time down there.
- Brilliant but Lazy: In the pilot, he passes up the chance to correctly answer a difficult question (despite Arturo yelling at him) because it didn't interest him. On the other hand, he took the time to read Arturo's papers that weren't assigned for the class because their contents did.
- Child Prodigy: Was skipped ahead two grades when he was 11.
- Didn't See That Coming: He was originally trying to invent anti-gravity, but accidentally created a wormhole to a parallel world instead.
- Disappeared Dad: His father died in an automobile accident when Quinn was very young.
- I Just Want to Be Normal: He resented his intelligence for years because it made him different from everyone else. (Being skipped ahead and thus smaller than his classmates didn't help.)
- Meaningful Name: Quinn is Irish for "wisdom, reason, intelligence" and Mallory means "unlucky." Pretty fitting for a smart guy who ends up being merged with his Alternate Universe duplicate.
- Mr. Fanservice: The show frequently has Quinn shirtless.
- The Nth Doctor: Played by Jerry O'Connell for the first four seasons, then briefly by an unknown actor in the Season 5 premiere before being replaced by Mallory.
- Really Gets Around: Had Ship Teases with Wade and Maggie, as well as plenty of one-off love interests.
- Team Dad: Becomes this after Arturo dies in late Season 3. Lampshaded in "Slither," where Quinn laments that, without Arturo, "It's all on me, and I'm flying blind."
- Took a Level in Badass: In Season 3.
- Two First Names: Quinn and Mallory can be either first names or surnames.
- Played by: Sabrina Lloyd
- Alliterative Name: Wade Welles.
- Back for the Dead: In Season 5's "Requiem."
- Break the Cutie: Three years of sliding takes a toll on her; Arturo's death is the moment that finally breaks her.Wade: (to Quinn) You know, when I first started sliding, all I saw was adventure. Now all I seem to see is death.
- Devoted to You: EVERY male character in EVERY dimension falls in love with her.
- Heroic Sacrifice: In Season 5's "Requiem," she sacrifices herself to save the other Sliders and stop the Kromaggs from acting on their plan to attack Kromagg Prime.
- Honor Before Reason: Frequently, much to the others' occasional irritation.
- Platonic Life Partners: With Rembrandt.
- Spell My Name with an "S": "Welles" or "Wells."
- Tomboy and Girly Girl: With Maggie in Season 3. Wade is the Girly Girl of the pair.
- Why Did It Have to Be Snakes?: In "Rules of the Game," she says she has a problem with being on airplanes.Quinn: Sliding between parallel worlds doesn't bother you, but flying does?
Wade: You have no idea how much.
- "The Dream Masters" reveals she was once robbed at knife-point, giving her a fear of knives and of being cut. She also has a problem with snakes, though apparently got over it by the time of "Slither."
- Played by: Cleavant Derricks
- Badass: In Seasons 4 and 5.
- Black Best Friend: To Quinn and later Wade and Maggie.
- Break the Cutie: He spent months in a Kromagg prison between Seasons 3 and 4.
- Conspiracy Theorist: "The Return of Maggie Beckett" reveals that Remmy always believed aliens landed at Roswell.
- Dirty Coward: In Season 1.
- Heterosexual Life-Partners: With Quinn.
- Hidden Depths: In "Eggheads," he recognizes a classical composer after hearing only a few seconds of a piece.Rembrandt: If you're gonna play the game, ya gotta appreciate the greats.
- It's All About Me: He was prone to this a lot in Season 1. He gets over it, though.
- Manchurian Agent: Revealed as one in Season 4's "Slidecage."
- Manly Tears: His nickname is "Crying Man," after all.
- The Nicknamer: But only to the Mallory brothers—"Q-ball" (Quinn), "Farm Boy" (Colin), and "Fog Boy" (Mallory).
- Odd Friendship: With Arturo.
- Platonic Life Partners: With Wade. Starting in Season 4, also with Maggie.
- Real Men Cook: In "Paradise Lost," it's stated he was a cook while serving in the Navy.
- Small Name, Big Ego: He has a lot of these moments in the first two seasons.
- Team Dad: In Season 5.
- Took a Level in Badass: At the start of the series, he was easily spooked by dangers on parallel worlds. By Season 4, he gladly fights Kromaggs hand-to-hand and mocks them to their faces.
- Why Did It Have to Be Snakes?: In "Slither," of snakes themselves.
- Played by: John Rhys-Davies
- Catch Phrase: The number of times he called someone a "blistering idiot" and yelled "Incoming!" at the end of a slide borders on this.
- Deadpan Snarker: Tends to react to things around him with either blustering anger or dry sarcasm. One example from the pilot, where everyone's shock at finding themselves in a Soviet-dominated parallel America is interrupted by the Professor's desire for lunch:Quinn: Professor, how can you eat at a time like this?!
Arturo: My stomach has no political preference.
- Disappeared Dad: According to "Into the Mystic," he's actually this to his son back on Earth Prime.
- Everyone Calls Him Barkeep: The others almost always address him as "Professor."
- Hidden Depths: Lampshaded in "Eggheads," as he talks about his dead wife and how encountering her double is stirring old feelings.Wade: I had no idea that you were such a romantic.
Arturo: And I had no idea that I would have the opportunity.
- I Just Want to Be Special: Season 2 introduced the idea that he resented Quinn for inventing sliding by accident.Fortune Teller: You resent the boy because it comes so easily to him.
- Jerk with a Heart of Gold: But virtually every single double encountered was a Jerkass.
- Last Name Basis: If the others don't address him as "Professor," then they do this.
- Like a Son to Me: Expresses this sentiment about Quinn in "Slide Like an Egyptian" after Quinn is believed dead.
- Missing Mom: According to "Season's Greedings," his mother died during a World War II bombing. While Word of God confirms that the Arturo that said this was the double from "Post Traumatic Slide Syndrome," their two worlds were described as so similar that the real Arturo likely experienced similar events.
- Redemption Equals Death: See Spot the Imposter below. The unscrupulous fake Arturo from "Post-Traumatic Slide Syndrome" ended up taking a bullet for Quinn.
- Secretly Dying: Introduced in "The Guardian," where Quinn finds out and is sworn to secrecy. Rembrandt finds out in "The Last of Eden."
- So Proud of You: He's not one to get emotional, but his admiration for Quinn always came through.Arturo: Every teacher goes through life hoping just once he'll have a student like you.
- Spot the Imposter: In "Post-Traumatic Slide Syndrome," the Sliders find themselves faced with two Arturoes each claiming to be theirs. The Sliders themselves have trouble figuring out who is who and Word of God ultimately confirmed what fans long suspected: the wrong one slid with them.
- Team Dad: Seasons 1-3.
- Played by: Kari Wuhrer
- Daddy Issues: Highlighted in "The Return of Maggie Beckett."
- The Heart: In Season 5.
- Jerkass: In her first appearance.
- Ms. Fanservice: In her season 3 appearances, she wore very revealing outfits, and the episode The Breeder pretty much speaks for itself. She slowly grew out of this in season 4, and stopped being this completely in season 5.
- My Friends... and Zoidberg: Her joining the team late Season 3 wasn't exactly warmly embraced, especially by Wade. Rembrandt points this attitude out in "The Other Slide of Darkness."
- Platonic Life Partners: With Rembrandt, starting in Season 4.
- Same Character, but Different: Her personality was retooled between Seasons 3 and 4. Lampshaded in the Season 4 premiere with a character with a personality of the Season 3 Maggie.
- Satellite Love Interest: Was dangerously close to being this in late season 3, when the production team thought of continuing the show with only Quinn and Maggie. Come season 4, her personality was rewritten and expanded to become The Heart, and in season 5, with Quinn gone, a Team Mom.
- Suspiciously Similar Substitute: Averted at first, as she was nothing like Arturo. Her Season 4 onward depiction does bear some similarity to Wade's, though.
- Team Mom: In Season 4-5.
- Tomboy and Girly Girl: With Wade and later Diana. Maggie is the Tomboy of the pair.
- Played by: Charlie O'Connell
- All of the Other Reindeer: On his adoptive world, the Amish-like residents treated him badly because of his inventions.
- Convenient Replacement Character: The only new character to avert this tropenote .
- Dropped a Bridge on Him: Possibly. See below.
- Fish out of Water: After spending most his life living in an Amish paradise, he has a little trouble adapting to more advanced universes for a while.
- Gadgeteer Genius: He built his own hang glider, for one.
- Put on a Bus to Hell: In "The Unstuck Man," Colin was made unstuck and left involuntarily sliding from one dimension to the next. At first, there was concern that Colin didn't survive, but he was generally treated as still alive and in need of help. By the end of the season, however, the characters acknowledged that Colin may really be dead, but it was nonetheless left ambiguous.
- Smarter Than You Look: Colin is rather naive, but only because he came from a less advanced world. He is nonetheless quite intelligent, adapting rather well to modern technology and figuring things out for himself.
- Wide-Eyed Idealist: As seen in "California Reich" and "My Brother's Keeper."Colin: You don't hurt someone to help yourself...at least you're not supposed to.
Quinn "Mallory" Mallory
- Played by: Robert Floyd
- Applied Phlebotinum: Geiger's experiments and combining him with Quinn allowed Mallory to walk again.
- Book Dumb:
- The Charmer: He can blend in with pretty much any social group, all it takes is a smile and telling an interesting story. He also tends to fall in love on a regular basis.
- Dark and Troubled Past: Including Parental Abandonment, a criminal past, and suffering from muscular dystrophy.
- Flip Personality: Mallory emerged as the dominant personality, but in "The Unstuck Man" and "Applied Physics," Quinn's personality and memories periodically broke through. By the end of "New Gods for Old," however, Mallory could no longer feel Quinn.
- I Owe You My Life: He is weary of Dr. Geiger, but acknowledges that without him, he'd still be in a wheelchair.
- Last Name Basis: Mainly because Maggie was incapable of calling him "Quinn," and then everybody picked it up. Even Diana, who knew him before Season 5's events.
- Parental Abandonment: His parents died when he was very young.
- Sharing a Body: With Quinn.
- Split Personality: In his first appearance, the original Quinn Mallory would sometimes resurface and talk through him. But after a few episodes, Quinn faded away, and Mallory was the only personality left.
- Played by: Tembi Locke
- Alliterative Name: Diana Davis.
- Black and Nerdy: She's black, and a scientist.
- Break the Cutie: Back-to-back episodes "Applied Physics" and "Strangers and Comrades."
- Heel-Face Turn: In the episode where she's introduced.
- Tomboy and Girly Girl: With Maggie. Diana is the Girly Girl of the pair, taking Wade's place in Season 5.