Voiced by: James Arnold TaylorThe show's protagonist and youngest member of the Test family. Johnny creates many of the show's plots through his willingness to abuse his sister's inventions or cut some corner in life. His best friend is Dukey, his (talking) dog. Occasionally Johnny fights crime using superpowers gained from his sisters under the name Johnny X.
- Aesop Amnesia: Johnny learns lessons. He just never remembers those lessons.
- Annoying Younger Sibling: And apparently, he's holding back. He once got his sisters to agree to do something by threatening to somehow be 100 times more annoying...it worked!
- Attractive Bent-Gender: Whenever he dresses like a girl.
- He briefly turned into a beautiful teenage girl during the pilot after using 'Mega Hottie Body Flakes'.
- Blackmail: In the early seasons, around how Johnny convinces his sisters for a favor, the blackmail usually being 'unapproved' experiments.
- Blah Blah Blah: What Johnny always says whenever Susan and Mary try to tell him how their invention works or warn him about overusing it.
- Book Dumb: Clever and manipulative, but a poor academic performer.
- Brilliant, but Lazy: He only SEEMS stupid, he's just too dang lazy to apply it to school or much else. However, if its something that has to be done or he really wants to do, he can come up with plans even his sisters find downright amazing.
- Basically its surmised that while his sisters got all the smarts, he got all of the creativity.
- Can't Get Away with Nuthin' : If Johnny uses some advantage for personal benefit, it will almost certainly backfire on him by the end of the episode. In a few instances, he has to use the advantage for the greater good, costing him his benefit.
- Good example is where he obtained x-ray vision to win at a gameshow, the prize being enough money to be set for life. Before he can actually select the suitcase and get the money, Dukey convinces to go and save the library from being taken by the mole people.
- Catch Phrase:"Whoa, Didn't See That Coming!""Say, wha-?""Now where have I seen this before?"
- Cosmic Plaything: More or less. How terrible his day is depends on the writer.
- Crouching Moron, Hidden Badass: The kids got a dunce streak in him. But he always saves the day.
- Ham-to-Ham Combat: Against many of his villains, particularly Bling-Bling Boy.
- Identical Stranger: Johnny looks exactly like Princess Mirabelle, so the SSGA gets him to take her place when the princess goes missing.
- Idiot Hero: In general, the mayhem caused in a good number of the episodes could have been avoided entirely if Johnny hadn't tried using the girls science to get out of chores or school or anything involving effort.
- Jerk with a Heart of Gold: He's an all right kid who still has growing up to do. He does do geuninely friendly things to try and help out.
- Kid-anova: He had a few girls crush over him.
- Manipulative Bastard: Johnny knows how to grift his parents and sisters to get his way.
- Nice Job Breaking It, Hero: Many of the episodes' main threat is his fault in some way. Though in his defense, he always tries to fix it in the end.
- Sensitive Guy and Manly Man: Manly Man to Dukey's Sensitive Guy.
- Stock Superpowers: As Johnny X.
- The Slacker: Johnny hates hard work and would rather lie, cheat and use his sisters experimental and often highly dangerous science than actually do the work.
- Spoiled Brat: Subverted. While he has to resort to Blackmail or begging to get what he wants from his sisters, they more or less often experiment on him as frequently and could be seen as a form of 'payment.'
- Unsympathetic Comedy Protagonist: It can get really hard to root for him.
Voiced by: Louis Chirillo (season 1-4), Trevor Devall (season 5-6)Johnny's talking dog who was genetically enhanced by Susan and Mary some time before the series. Dukey's main job is to act as Johnny's voice of reason even if he's prone to being ignored. That said, he's more than capable of doing the wrong thing himself if properly motivated (such as with steaks). On more than one occasion he acts as a crimefighter alongside Johnny under the monikers Super Pooch, X Pooch or Super Dukey, though after the earliest incidents he expresses a dislike for doing so.
- Action Pet: He is a black-belt in Kung-Fu.
- Berserk Button: Harming, trying to kill and/or being responsible for Johnny's mortality in front of Dukey.
- Brought to You by the Letter "S": On his Super Pooch costume, although the letter is D which appears nowhere in his Super Pooch name.
- The letter in this case is a holdover from when his alter ego was called "Super Dukey". The writers have since flip-flopped on exactly what his superhero handle is between "Super Dukey", "Super Pooch" and "X Pooch".
- Catch Phrase: "I'm a kid with a rare hair disorder".
- Cowardly Lion: Dukey will never miss an opportunity to complain and cower, but he comes through in the end.
- Deadpan Snarker: When you hang around with Johnny, it comes naturally.
- The Drag-Along: Most of the time unless the situation calls for it.
- Gasshole: And he's not too shy about it either...
- Hypercompetent Sidekick: Borderline Beleaguered Assistant. However, his reason of doing matters is only out of being forced to go or Johnny's safety, being Brilliant, but Lazy
- Martial Pacifist: Susan and Mary included the DNA of Kung Fu masters in his genetic code, making him a skilled martial artist...however, he doesn't like using it and more often would just prefer to stay at home and goof off than fight supervillains. He also refuses to teach it to Johnny since he knows Johnny doesn't have enough self control not to use it.
- Master of Paper-Thin Disguise: Works due to most people in their world being stupid. He normally just says he's a 'kid with a rare hair disorder' and they believe him. He also sometimes wears a t-shirt that says Not A Dog.
- Morality Pet: Played with in the fact that although he tried to convince Johnny something is wrong (or right) to do, he often fails at changing Johnny's mind unless it has to do with his family. Also tries to convince the Sisters that treating Johnny like a guinea pig is wrong. Fails in that as well.
- Only Sane Man: Though most anyone looks sane next to Johnny.
- Sensitive Guy and Manly Man: Sensitive Guy to Johnny's Manly Man.
- Trademark Favorite Food: Dukey would do anything for a steak. Or Bacon
- Also enjoys coffee.
Susan and Mary Test
Susan Voiced by: Maryke Hendrikse
Mary Voiced by: Brittney Wilson (season 1, 5); Ashleigh Ball (season 2-4, 6)Johnny's older twin sisters who attend the Mega Institute of Technology. Both are geniuses capable of devising whatever machine the plot demands and most episodes relate at least partially to one of their experiments. Both Susan and Mary have a crush on local boy Gil that can work against them. Susan is also the object of affection of resident villain Bling-Bling Boy. Both sisters look identical except for their fashion choices (Susan wears squared glasses, a skirt and knee socks and has straight hair; Mary has curved lenses, wears jeans and has curled hair).
- A-Team Firing: Once. Mary attempted to hit a transformed Dukey with the needle containing a serum that will turn him back to normal and every shot hits somewhere on the wall around him.Mary: Man I am a lousy shot.
- Agent Mulder and Agent Scully: Mary and Susan, respectively; they even have the same first letter initial.
- Balloon Belly: Not as often as Johnny or Dukey, but they will gorge themselves on occasion. One time they fattened themselves up with candy, and another they got bloated from eating too much ice cream.
- Catch Phrase:
- "We're such geniuses." Well, in the first seasons anyway.
- And "*sighs* Gil, next door".
- Cut Lex Luthor a Check: A non-evil example. The only reason they bother inventing things is to get Gil to notice them. When he says that he's moving away, they immediately shut down the lab forever, and Johnny takes it upon himself to try and stop Gil from moving.
- Dogged Nice Girls: They try their best to win Gil's affections though he doesn't seem to notice them. Admittedly, they do go to some creepy lengths.
- Failure Is the Only Option: Their attempts to attract Gil attention always end in failure.
- Fiery Redheads: Susan tends to be more irritable than Mary is, which often leads to her downfall.
- Love Makes You Crazy: Their attempts to get Gil to notice them always backfires or screws up. Not to mention fighting one another over who will marry Gil, ending up with them becoming a couple of messes, which derives Gil's attention to Johnny.
- Magic Skirt: No matter what she does, Susan's skirt doesn't seem to ever move. Not even if she's sliding, falling, or doing cartwheels.
- Nice Job Breaking It, Hero: They end up causing the disaster of the week as often as Johnny, and more often than not end up needing Johnny's help to fix it.
- Not So Different: Susan and Mary's ploys to get Gil's attention can be eerily similar to Bling Bling Boy's attempts to get Susan. For example, they both turned themselves into babies to be sat by their crushes. Interestingly enough, this has not been pointed out as of yet.
- Punny Name: Mary and Susan Test.
- Red Oni, Blue Oni: It's subtle but it's there. Susan is the red: more rational minded, always tries to see if there's logical explanation for everything and can be rather stubborn. Mary is the blue, willing to believe more in the unnatural and is usually the voice of reason between the pair. There's also a dash of Tomboy and Girly Girl with the way of dress (Susan wearing a skirt and Mary Janes while Mary wears jeans and sneakers.)
- Redheaded Hero: Both of them of the Science Hero type.
- Single-Target Sexuality: They are only interested in Gil even though he's a Dumb Blonde who clearly has no interest in them or even awareness that they exist, no matter how hard they try to get his attention.
- Smitten Teenage Girls: They both have a crush on Gil.
- Slapstick Knows No Gender: Especially Susan.
- Sweet Tooth: One episode showed they have a stash of sugary junk food hidden in their lab.
- Twin Threesome Fantasy: Somewhat averted Depending on the Writer. Sometimes the twins are shown to be open at the idea of sharing Gil, but there are episodes when they fight each other to be the only girl he has eyes for. Marriage seems to be the touchiest point; dating and making out not so much.
Voiced by: Andrew FrancisA pleasant local boy who's friends with Johnny. He's the romantic target of both Susan and Mary, though he can never seem to remember their names.
- Ambiguously Bi: Shown to clearly crush on girls, but seems oddly fixated on Johnny over his twin sisters.
- Brainless Beauty: The boys head is hollow as a coconut.
- Catch Phrase: "Hey, Johnny!", or "Tell Johnny I said hi!" whenever Johnny's not around.
- Dumb Blonde: Even more than Johnny. Implied to have once possessed at least average intelligence; repeated memory wipes by Susan and Mary to cover their bungled attempts to woo him, have left Gil with severe brain damage.
- Laser-Guided Amnesia: A rare naturally occurring case. He pretty much never remembers Susan and Mary's names even though he knows their younger brother.
- Oblivious to Love: Like you wouldn't believe...
- Prehensile Hair: As a member of the Johnny Saving Six.
- Surfer Dude: Blonde, tanned, and frequently spouting surfer lingo like "Cha."
Eugene "Bling-Bling Boy" Hamilton
Voiced by: Lee Tockar
- Abhorrent Admirer: He loves Susan Test but she wants nothing to do with him due to his repulsive appearance and overbearing personality. In one episode, Eugene was given a potion that made him stop loving Susan. He started loving her sister instead.
- Bodyguard Babes: Initially had some red-haired female designed androids that acted as his enforcers and they appeared infrequently through the first two seasons before they were never seen again for the rest of the series.
- Casanova Wannabe: Try as he might, the kid ain't a ladies man.
- Disappeared Dad: Never been mentioned once.
- Ditzy Genius: His obsession with Susan and reliance on hired scientists can make you forget he's as much a super-genius as Susan and Mary.
- Friendly Enemy: When the super-villains capture Johnny, he admits Johnny is the only one who can stand his temper tantrums and goes to rescue him.
- Insistent Terminology: He hates being called by his real name, Eugene.
- As of now, he doesn't even bother correcting people anymore.
- Murder the Hypotenuse: Bling-Bling plotted to get rid of Gil so Susan would focus her attention on Bling-Bling Boy.
- Not-So-Harmless Villain: While his attacks normally revolve around getting Susan to be his girlfriend, when he snaps on occasion, he is extremely dangerous. Never underestimate a genius with infinite funds and a huge army at his disposal.
- Only Friend: Johnny may be his Arch-Enemy, but he also doubles as Bling-Bling's only friend. As it's pointed out above, Johnny is the only person who can stand him.
- Stalker with a Crush: Has a huge crush on Susan.
Voiced by: Ian James Corlett
- Abusive Parent: Several episodes have him stating what kind of punishment he plans to give Johnny, many of which are rather cruel. In fact, it is implied in multiple episodes throughout the series that he actually hates Johnny (despite constantly saying he loves him), and will take any opportunity to get rid of him.
- House Husband: He is literally a "house husband."
- Lethal Chef: By how much is by Rule of Funny. He is capable of making tasting food, but he loves making meatloaves and somewhat treats it like an art form though that doesn't mean the meatloaf will be tasty (least to anyone but him.)
- Skewed Priorities: In an episode where Johnny breaks his foot, Hugh is more concerned about the family's insurance premiums going up.
- The Scrooge: An interesting example of this despite not being the breadwinner of the family and lacking the usual reason a dad would have for this.
- Trademark Favorite Food: Meatloaf. Hugh rarely ever cooks anything 'but' meatloaf, and will go to great lengths to not cook anything else but meatloaf. He clearly chooses to ignore the glaringly obvious fact that no one but him likes it, even when his family wretch with horror at the sight of it and Johnny openly states no one else likes it.
- You Are Grounded: He threatens to ground his kids for life constantly.
Voiced by: Kathleen Barr
- Mama Bear: She wouldn't let anyone hurt her kids, that goes for Johnny, the Girls and Dukey.
Voiced by: Brittney Wilson (season 1, 5); Ashleigh Ball (season 2-4, 6)
- Distaff Counterpart: Her design and attitude is essentially a female Johnny, though she's presented as more mature.
- Ship Tease: With Johnny, with it repeatedly made clear the two do have feelings for each other.
- Tsundere: Sissy tends to hide her crush very well through bullying Johnny and asserting superiority over him.
Voiced by: Scott McNeil
- Hidden Depths: Apparently likes caring for roses.
- Taken for Granite: His power as a member of the Johnny Saving Six.
Janet Nelson Jr.
Voiced by: Kathleen Barr
- Demoted to Extra: She was only seen for the past few episodes in Season 1 before she was demoted to a background character in later episodes.
Mr. Black and Mr. White
Voiced by: Bill Mondy and Scott McNeil, respectively
- Catch Phrase: What's their favorite vacation spot? "We are going to Fiji! We are going to Fiji!"
- Heterosexual Life-Partners: Although the "Heterosexual" part drops dangerously low at times.
- The Men in Black: Kinda. They don't exactly do much good when they even appear. Usually they end up coming to Johnny, Dukey, Susan, and Mary for help.
- Salt and Pepper: Mr Black is white, Mr White is black.
Voiced by: Louis Chirillo (season 1-4); Bill Mondy (season 4-5)
- Card-Carrying Villain: He is well aware he was evil, though sometimes wishes he wasn't.
- Drink Order: He loves ice coffee.
- Heel–Face Turn: Brain Freezer seems to have dropped his evil ways since taking a level in handsomeness.
- Pungeon Master: Enjoys making bad cold-related puns.
- You Need to Get Laid: A recent episode shows that after acquiring good looks and a new coffee shop, he is much less interested in taking over the world and revenge.
Voiced by: James Arnold Taylor
- Evil Sounds Deep: Via his bee suit when he has the helmet on.
- Heel–Face Turn: His only goal was just getting kids to eat healthier via his granola bars which Johnny eventually admitted didn't taste so bad. When Johnny attempt to do a improptu candy-giving holiday during the summer season failed for various reasons ( lack of a good mascot, being sued by the Easter Bunny etc), Beebles had the resources to do the holiday without any of the flaws (has a recognizable name, bees that could help him give away free granola bars and get kids to eat healthier in the bargain). Once he was able to achieve that, he no longer had a grudge against the Test siblings.
- Verbal Tic: Puts an emphasis on any instance of "be" that comes up when he talks.
- Well-Intentioned Extremist: In his first appearance, one of his main motives was to get kids to start eating healthier by stealing all of the sweets in town.
Voiced by: James Arnold Taylor
- Darth Vader Clone : Though he's more like Vader parody Dark Helmet, from Spaceballs. They have similar motivations and their actual appearances are similarly dorky looking.
- Even Evil Has Loved Ones: His one main redeeming trait is that he does genuinely care about his daughter.
- Laser Blade: What do you expect? He's a parody of Darth Vader or maybe Dark Helmet.
- Trademark Favorite Food: TOAST! (Note that he only learns about toast later in the series.)
- Villain Decay: Justified as the result of living on Earth, as he can't replace his weapons which are from his own planet.
- Well-Intentioned Extremist: In his original appearance, he only destroys other planets to sustain his own planet (though apparently, this isn't really needed). After that, he's more in it for revenge.
Voiced by: Lee Tockar
- Corrupt Corporate Executive: He's the head of a toy company named after him, but devotes all his time to finding ways to get rid of kids.
- Cut Lex Luthor a Check: Averted, sorta. His board of directors asked him if they'd go out of business if his plan succeeded. Turns out he'd already thought of that and programmed his robots to offer to 'babysit' the kids for free to keep their parents happy. Still, he's a brilliant enough man that his smarts could be better spent elsewhere.
- Devil in Plain Sight: His company is still afloat despite him being obviously psychotic and his company producing extremely dangerous toys with the intent to maim or 'get rid of' kids. Handwaved in that his legal team is apparently extremely good.
- Disproportionate Retribution: He built an army of extremely powerful robots to imprison kids in their own houses just for annoying him.
- Legion of Doom: He's the leader and founder of the 'Johnny Stopping Evil Force Five'.
- Would Hurt a Child: His entire character is this.
Voiced by: Maryke Hendriske
- Precocious Crush: A rare reversion: Jillian, who is five years older than Johnny, has a crush on him.
- Rebellious Princess: Dark Vegan's daughter. Doesn't approve of his destruction of other planets.
Voiced by: James Arnold Taylor
- Evil Counterpart: To Dukey in that he was given his intelligence and human-like traits with the exact same method as Dukey did. He's just a lot more motivated.