Absurd Altitude: An amusement park ride meant to deter Johnny from having an amusement park at his house.
Accidental Public Confession: The Moonsies do a Type 2 when Johnny and Dukey see their plans to invade the Earth; it's a Type 2, because although Johnny and Dukey see the plans, they don't understand them because they can't read Moonsie.
Affably Evil: a decent amount of the villains can be surpisingly sociable when they aren't trying to take over Porkbelly or kill Johnny, to the point where they genuinely enjoy competing in Johnny's races and such. Notably Darth Vegan, despite being one of the most evil villains in the series, is more of a Bumbling Dad when he's not after Johnny's head. Albert is a notable example as well, Justified since as Tim burnout's butler, Mr. Mittens forces him into his schemes and he genuinely bears no ill will towards Johnny.
A.I. Is a Crapshoot: When Susan and Mary build boy-borgs to make Gil jealous, they become * very* possessive of the twins.
Later happens to Johnny's new smartphone in "iJohnny", and the Super Smarty Pants.
Pretty much anything that the girls make with A.I. will turn evil save for something that Johnny's supposed to immediately break.
Also anything the military makes in Area 51.1, like the look-alike cyborgs in "Johnny Johnny" and the super soldiers in "Johnny X Strikes Back Again".
Ambiguously Gay: Dukey has shown a few signs of it. The very first time he was shown, he was wearing biker leather and enjoying it. Also, when he nonchalantly explains male dominance and let's not forget when Susan and Mary brainwashed him in that one episode. One time he was turned into a cheerleader and said that he felt pretty and, of course, Seńor Smoothy-Buns. He has even been shown doing the limp-wrist. Dukey almost admitted it in the episode "Johnny's Supreme Theme," when Johnny was swindling his sisters by saying that they should practice to impress their leading man. Then, Dukey replies with "Yeah! I always practice to impress my leading ma—I'm gonna stop talking now."
More so Gil. In one episode, Johnny dresses as a girl and Gil doesn't notice him. He stated once how he didn't like cookies but loved Johnny. He only really pays attention to Johnny and not really anything else.
Actually he seems to be bi. In the sleepover episode he chases after Jilian, the "hot green haired girl", much to Susan's dismay.
Archived Army: Johnny brought back several historical figures, including Attila the Hun and a caveman, to create the most powerful hockey team.
Art Evolution: Season 1 is significantly different compared to the rest of the series.
Which is due to switching from traditional animation to Flash: the first season was animated at Warner Bros but budget cuts from the merger of the CW and the WB forced the animators to a new studio (Cookie Jar Entertainment) and format for the second season.
Ascended Extra: Montague Mouse, who debuted as a gag character in a season four episode to playing a part in several episodes later.
Interesting example with Hank Anchorman in season 2 and beyond; he appeared as a one-off character in "Johnny's Pink Plague" in season 1, then became a recurring character in season 2 with his previous design replaced by a human version of the unnamed robot anchorman in "Sonic Johnny", who was also a one-off character. Two one-off anchormen merged into one!
Author Appeal: Gender-bending and crossdressing (usually of the male-to-female kind) play huge roles in many episodes.
Batman Gambit: A trap set by Dukey to capture Johnny's Evil Twin requires that the Good Twin reveal the trap to the evil one and the evil twin to step contemptuously over the trigger - at which point he steps right into a different trap.
Broken Glass Penalty: One episode goes through all the variants of this trope when Johnny accidentally ticks off a crazy man in one episode, and goes through a variety of completely pointless and ever more complex plots to try and get the ball back.
Chekhov's Gun: The incinerator that Janitor Dukey uses to burn trash throughout the wood shop episode. Guess how they stop the rampaging turbo-wood-bench.
Johnny: Incinerator! Coooooool. Can we burn something? Dukey: Maybe later.
There was also Hugh's terrible cookies in one episode, in which Johnny mentioned tasted worse than dirt; later on, when warthogs attack Porkbelly, the gang uses the cookies to send them back to eating dirt in the desert, which again, tastes better.
Child Hater: Wacko, who is ironically a toymaker for children. The products he usually builds are designed to get them out of his life.
Continuity Nod: In the episode 'Who's Johnny?', before the final sequence returning Johnny to his original personality, Johnny changes personalities contained in his genetic code every time he gets hit; one personality he gets is of a dog, with the same design when the girls altered his DNA to make him a dog in an early episode.
Could Have Avoided This Plot: Many of the troubles in the show could have been avoided if Johnny just did what he was asked, instead of using his sister's inventions for a shortcut.
Crossdresser: In Episode 41a: "Join the Johnny Scouts", Johnny becomes a Girl Scout and tries to sell 1,000 boxes of cookies to get a new bike. His father is clearly uncomfortable with this and Johnny tells him that "you said you'd love me and accept me no matter what", but he is using this situation to bribe his father into buying the last 37 boxes of cookies.
Gil also buys a box of cookies because: "I hate those cookies, but I love you Bro-man!".
Not that kind of love. He asks Johnny earlier in the scene what's different about him. Johnny deadpans "I'm a girl.", and Gil goes "Nooo, that's not it."
He also does it in "Take Your Johnny to Work Day" and does so again in "Johnny Dodgeball", albeit that time it was reluctantly.
Also in the episode where Mr. Mittens was introduced and Johnny and Dukey were tricked into it.
Not that other characters don't do it too. Let's see, Dukey's done it, Gil's done it, Mr. Black's done it, etc...
Dude, She's Like in a Coma: Susan and Mary want Johnny to invite Gil over for a sleepover so that they can kiss him while he sleeps; on a similar note, Bling Bling insists that Johnny invite him as well so he can kiss Susan while she sleeps.
Even Evil Has Standards: When Zizrar plots to steal the Porkbelly Library, he send the authorities a letter warning them about what he's doing after the setup is complete because although he wants to make the humans stupid, he doesn't want to hurt anybody.
Everybody Laughs Ending: A number of episodes, but the third season ending is notable for the villain of the piece joining in the laughter until he lampshades it. Then he swears revenge.
Expy: A parody of Fred appears in an episode involving the characters trying to find instant fame from posting videos online like him after seeing him become rich and get a movie; in the end, they see the character's movie is terrible because its only gimmick was he had a squeaky voice.
Mary and Susan: We... might have used too much DNA.
Flamboyant Gay: Nobeard and his pirate group, as well as the Mole-People.
Fluffy Dry Cat: This happened to Dukey after he fails to thwart an evil pair of paints who have taken over the titular character's mind.
F Minus Minus: Extra Credit Johnny and Johnny's Z-, and later ZZ-.
Forgotten Birthday: In the episode "Bath Time for Johnny", Dukey thinks that Johnny forgot his birthday.
Four-Fingered Hands: Lampshaded two different times. Once when Susan waved her pinky around when trying to indicate the number four on one hand and other when the General up another finger on the other hand to represent the number three.
"Freaky Friday" Flip: Hugh and Johnny complain that the other has an easier life so to prove it, they switch bodies with Mary and Susan's help; at the end of the episode, after they've learned how hard each others' lives are and switch back, Susan and Lila get into the same fight and switch places as well.
Friendly Enemy: Johnny is on surprisingly good terms with his Rogues Gallery when they're not trying to destroy him. Go Karting with Bowser examples aside, he's also gone to them for help now and again. Bling Bling Boy once mentioned that he liked Johnny, seeing a lot of himself in the boy. And then there's the time Johnny tried to get Brain Freezer a girlfriend.
Gender Bender: Quite a lot, even from the very first episode where Susan and Mary have him test 'Hottie Body flakes' which turns him into an attractive teenage girl for a few seconds before turning into a giant ugly girl monster.
The next time it was so prominent was when the girls deliberatly turn their brother and dog into muscular twenty something Roller Derby competitors. The device was even called the gender bender.
When did we land in a bad [decade] [genre] [medium]?
When Johnny and Dukey are transported into a fantasy story and called Chosen Ones, Johnny reassures Dukey that they'll win because Chosen Ones always win; subverted when it turns out to be a simulation and they were playing against Susan and Mary, but he gets points for trying.
Johnny in a recent episode: when he wins a cruise in a contest he never entered, he instantly realizes it's probably a trap and comes Crazy-Prepared (and, without them knowing, makes sure everyone else was as well); naturally, he was right.
Johnny Cart Racing is a homage to Wacky Races, complete with the villain team (Brain Freezer and Mr. Mittens in place of Dick Dastardly and Muttley) stopping when in the lead to try and keep the others from finishing with nefarious schemes. This was also lampshaded by an increasingly frustrated Mr. Mittens.
As well as the old Wile E. Coyote cartoons, with Johnny and Dukey as the Roadrunner(s) and Bling Bling as the Coyote.
The episode "Old School Johnny" parodies the first and the third Back to the Future movie.
A whole episode referenced the works of Dr. Seuss.
Humiliation Conga: Bling Bling gets one in Johnny Cruise. After his plan to get Susan Goes Horribly Wrong and nearly gets everyone killed (which was pretty unhinged to begin with, even for him), Johnny forces him to personally perform every job on the entire cruise for his family in a rather humiliating manner. However, in this case, it was well deserved.
Hypocritical Humor: While using a machine that turns base metals into gold, Hugh Test yells at the girls for inventing such a device.
Ironic Echo: Johnny makes a speech to guilt Dukey into going on a field trip because Johnny needs parental supervision to go; Dukey then uses almost the exact same speech to get Johnny to help free some animals later in the episode.
Not really, Johnny actually isn't that stupid... just really, really immature: he usually can outsmart his sisters/parents if sufficiently motivated; his sisters even comment in one episode that he's actually pretty smart.
Long Title: The Say-Goodbye-To-Johnny-Blow-Out Bye-Bye-A-Palooza-Jamfest Super-Send-Off Party Jam.
Long Runners: By the standards of Cartoon Network, at least. Six seasons long, and the first show ever on Cartoon Network to come close to cracking 200 episodes.
Loophole Abuse: In the first episode Dukey points out to Johnny that Hugh told him "touch [his camera] and die", after which Johnny states he's not physically touching it, since he's operating it using a stick.
Lost Aesop: "There's a lesson in all this, but darn if I know what it is."
Also this exchange from the episode "Johnny Cruise", after Eugene reveals his plan to deliberately sail a cruise ship full of passengers into an iceberg so that he can heroically and romantically rescue Susan as it sinks:
Johnny: Are you nuts?! Eugene: Close, I'm in love.
Mid-Battle Tea Break: While "playing" a game of Uncle where each person beats the hell out of the other to get them to say "Uncle", Johnny, Dukey, Susan and Mary stop in the middle to have snacks.
Mystery Meat: Johnny's dad's horrible meat loaf recipes. Doesn't just serve meatloaf by itself, he also serves it in burritos, tacos, etc. Every proclamation of Mr. Test's meatloaf for dinner is met with screams of horror from his family.
One episode hints that there isn't anything in there that can be remotely called meat. He doesn't seem to try and hide that either.
Never Say "Die": Played straight for the most part, but weirdly averted in "Johnny's Royal Flush" where a gator is heavily implied to have been chopped up in Porkbelly's sewer system and turned into luggage
The actual word "die" - not to mention the word "kill" - is averted, however. Johnny's enemies always wants to "destroy" him.
What about in "Deep Sea Johnny" when it was implied that the octopus was killed and served as sushi?
Also in "Johnny Testosterone" Mary and Susan mention their dad will Kill them if anything bad happened with Johnny.
Noodle Incident: Several. Occasionally used as Blackmail by Johnny or a reason they can't do an experiment without getting in trouble with Dad. For example, experiments somehow resulted in a gigantic Johnny bursting out of the roof of the Test house and shooting lasers from its eyes...twice.
Packed Hero: Subverted. Johnny and his friends visit an ice cream factory, and Johnny's dog is thought to have fallen into the vat and been packed into a tin. After Johnny eats his way through the entire batch, the dog walks up to him and asks Johnny what he's doing.
Pun: The Bee Keeper's and Brain Freezer's puns related to bees ("Bee afraid! Bee very afraid!") and cold ("Time to chill out!"), respectively. The latter is most likely a reference to Mr. Freeze from Batman & Robin.
Revenge: A lot of Johnny's enemies are obsessed with getting revenge on him. And less on their own schemes. And most of their revenges are for their previous revenges being foiled by Johnny himself.
Reverse Polarity: Averted when Johnny uses a fruit revitalization ray to bring back Porkbelly's founding fathers as zombies because the ray only works on people halfway. Susan reverses the polarity on the ray to de-animate the founding fathers but it doesn't work because they're already sort of dead.
Rube Goldberg Device: Dukey builds one of these to trap Johnny's Evil Twin. Subverted when the Evil Twin figures out the trap and steps over the trigger... into the actual trap which is a covered hole in the ground.
Rump Roast: One of the actions when Smarty Pants gets jealous about Johnny seeing other girls is that they get so hot in the rear area that Johnny has to jump out of them.
Running Gag: Dukey is stated to have money saved up 'for a rainy day.' It's referenced commonly enough to be used as a plot point every now and then. Just how much he has saved up tends to vary wildly, though.
Salt and Pepper: Subverted with Mr. Black (The white guy) and Mr. White (The black guy), whom seem to have little difference personality-wise.
Sarcastic Confession: Hugh Test angrily demands to know if Johnny lost his phone, so Susan tells their dad that they're looking for Johnny's phone with baseball bats because they want to smash it before it takes over the world. Which they are.
Screw Yourself: In the episode "Johnny Alternative", it's strongly implied that Johnny has fallen in love with what is obviously a female version of himself.
Though that seems more like "you TOO can have this nightmare house, but it won't come with the SUPER FUNNY ENDING we have here!"
Selective Obliviousness: Hugh Test clearly chooses to ignore the fact that nobody likes his cooking, regardless of horror struck faces, audible gagging, running to vomit and being told to his face that his cooking is aweful. The most he ever said about people opinion of his food is "I'm beginning to think you people don't like my meatloaf."
One of the early episodes had a toy series called Roboticles. Coincidentally, Johnny's voice actor would later voice a character in the actual series, while some of the other voice actors have already been in other BIONICLE movies.
At the end of "Johnny vs. Bling Bling 3", Johnny steals a page from John McClane's book (specifically, "surrendering" with a weapon taped behind him).
"Johnny Test's Quest" not only was the episode a direct reference to Johnny Quest (Including Mr.White dressing up in Hindi clothing.) but wouldn't be surprising if the episode was only made as an in-joke because the names sound similar.
Screechereen is a combination of (Shadow) Lugia, the legendary birds, Gyarados, Mew (may or may not exist), Missingno (may or may not exist), and Pikablu, Nidogod, etc. (may or may not exist). Also, in general, flying Pokémon are superior for some reason.
The second Tinymon episode contains reference to Digimon, with de-evolving and Jogress.
Single-Minded Twins: The twins avert this but avoid being Polar Opposite Twins. They do not wear the same clothes and hair styles, and have different voices, but don't have exact opposite personalities. A very rare case of a cartoon making (relatively) normal identical twins.
Snowlems: The Brain Freezer attacks Porkbelly with a whole bunch of them.
Space Whale Aesop: The show throws an Anviliciousvideo games rot your mind Aesop by having Johnny be unable to stop thinking about inanimate objects becoming random monsters. Which would be completely unimportant if his sisters didn't get a "make imagination real" helmet stuck on his head.
Played for Laughs at the end of "Johnny-itis", in which Dukey tells the audience to "never drink isotopes."
Spoiled Brat: Surprisingly subverted. Johnny's attempts of getting his sisters' to help him through blackmail are balanced out (or possibly even caused) by his sisters' experimenting on him without permission. Been hinted to have happened since Johnny was a young child.
Spoofing Spoofiness: Dark Vegan and the episode he debuted in, "Johnny Test in Outer Space", were parodies of Dark Helmet and Spaceballs respectively, which in turn were parodies of Darth Vader and Star Wars.
Spot the Imposter: When the military builds a Johnny Cyborg, it invokes this trope to avoid being shot by Dukey.
Stating the Simple Solution: Played with in the first episode with Mr. Mittens. His butler ask why his Doomsday Device needs a timer and instead of just setting it off now. The Genre Savvy Mittens explains it's to get him out of range so he can remain and continue to take care of him.
Occurs more frequently with Dukey asking the Brilliant, but Lazy Johnny why he doesn't just do his assignments instead of trying anything but.
Sure, Let's Go with That: Susan and Mary use this when Hugh claims that Johnny is having an allergic reaction to the meal he made. The truth is that Johnny's brain has been devolved due to an experiment.
Take Over the City: Lampshaded when Mr. White & Mr. Black ask why the show's villains always seem to attack Porkbelly.
Take That, Us: When confronted with the cartoon "Dog and Bone" which has a near-identical premise to his life, Johnny simply asks "Who'd want to watch something like that?" before glancing at the fourth wall.
Tempting Fate: Any time anyone says "We're safe! We're all safe now!" is a cue to the universe that it's time to make them unsafe again.
This Is No Time for Knitting: Johnny — confronted by some giant moon-men — hastily makes paper planes and throws them to poke the giants in the eyes, but not before Dukey scolds him for making paper planes.
Gil, not just the fact he is completely oblivious to Susan and Mary's existence, but he once started a babysitting service despite he knows nothing about babysitting. (Jumping on a small pull-out couch with the baby-fied Susan and Mary, feeding them chili, and watching a horror movie in front of them) "Babies like chili right?"
Totem Pole Trench: Susan and Mary do this to get into a top secret lab. Johnny and Dukey use this to try and get past the ski captain to shred the Behemoth.
Trademark Favorite Food: While meatloaf certainly isn't the favorite food of most Test family members, it's obviously the favorite of Hugh's - since he's making it every night.
Described by Dukey as "dry as a desert muskrat."
Dukey will do anything for steak.
Dark Vegan and toast. He spends one episode trying to get home to Vegandon, only to find out there's no toast there. So he immediately returns to Earth. Another episode he plans to destroy the home planet of the Rib-eye Knights because he can't keep from burning his toast. Once Johnny shows him how to do so, he immediately drops the plan and befriends the Knights.
Though they seem to vary on whether they actually want to share him or not. Discussed briefly in the episode "Johnny Two-Face", where Johnny was given a second truth-telling mouth that revealed the uncomfortable truth the girls:
Mouth of Truth: ...you're not smart enough to realize there's only one Gil and two of you. And you both can't have him. You know that, right?
Tyop on the Cover: The title card of the episode "Johnny Get Yer Gum" actually says "Johhny Get Yer Gum."
A possibly intentional in-universe example is "Game Galaxie".
Uncanceled: Teletoon had ordered and shown new episodes after a year lull and recently Cartoon Network has been showing these new episodes.
Between the various hockey references (including scenes of Johnny and other kids playing street hockey, and hockey apparently being Johnny's favorite sport), and its closeness to the Canadian border in "Johnny Moustache", it's possibly in Minnesota.
According to the flag flying above the school in "Old School Johnny"... Ontario.
Most of the show was done by Teletoon, a Canadian company, so they probably got lazy and put it in Ontario; despite things like the CIA and the Area 51 knockoff, and the White House...
It wouldn't be the first time Teletoon moved a series from the United States to Canada when they took over it's production - see What's with Andy?.
One episode includes a California flag for some odd reason. So... does this mean that the show is back in the US, or is Canada screwing with us?
In one newer episode Johnny makes an excuse that Dukey is his relative from Canada so it seems it's set in the United States.
Who Would Want to Watch Us?: "Dawg & Bone" is an in-universe cartoon about a boy who has genius twin siblings and his dog and the adventures they have together. Johnny and Dukey consider the show lame.
Wildcard Excuse: Dukey the speaking dog is always "a kid with a rare hair disorder".
William Telling: One episode, "Dolly Johnny" has Johnny practicing shooting plungers at the apple perched on Dukey's head. He fails to hit the apple until he has to shoot something else that's more important.
With Great Power Comes Great Insanity: In the episode where the Test kids and Dukey play chess with the chess pieces brought to life, Johnny takes the role of the king. When he took a liking to chess, the title went to his head and the orders he made go from making moves on the board to terrorizing Porkbelly; this is known to the characters as "The King's Madness".
Yandere: In one episode, Johnny asks his sisters for super-intelligence. He obtains a pair of pants, which become self-aware... and this.
The girls create three robot boys to make Gil jealous. It works. In both directions.