Johnny Test mostra as aventuras de um garoto corajoso de 11 anos, seu cachorro super-esperto e falador Dukey, e suas duas irmãs gêmeas, cientistas geniais, Susan e Mary, que usam Johnny como cobaia para suas experiências a fim de impressionar o vizinho Gil, que nunca as percebe mas é grande amigo de Johnny.
James Arnold Taylor • Maryke Hendrikse • Ashleigh Ball • Lee Tockar • Ian James Corlett • Trevor Devall • Kathleen Barr • Scott McNeil
Things have been mysteriously disappearing underground, making Johnny and Dukey believe that the people behind this are "mole people". When Johnny accidentally loses his dad's new camera, he must journey to the center of the earth to retrieve it before dinnertime, or he will be grounded.
Susan and Mary give Gil a piece of their special love "bubble gum", but by accident, it makes him transform. In order to save Gil and the others in pork belly, they have to give Johnny and Dukey some cool super powers.
Bling-Bling Boy has stolen a device that turns things into gold and Johnny must get it back before dinnertime.
Johnny tries to get his baseball back from an old man before the baseball game starts.
Susan and Mary are having a party and use a device on Johnny in order to make him look good so all the girls at the party will love him, but Johnny turns into a monster.
The Extreme Teen Team are on the loose and it's up to Johnny to bring them down.
Johnny uses an invention to breathe underwater, yet sharks and electric eels begin to walk on land and wreak havoc to the beach.
Bling-Bling Boy steals a backpack and Johnny must retrieve it so Susan and Mary can show it off at the school science fair.
Johnny goes back in time to ask Thomas Edison for a hockey invention and then to gather all of the vicious and ruthless "legends" he could find, in order to form a hockey team which will help the Ice Pigs win a game.
Johnny fills the house with some of Hugh's favorite things listed in his notebook. However, Johnny learns that the book was also full of Hugh's least favorite things (most of them scary.) To make matters worse, Lila's boss is coming over for dinner that night.
Johnny wears super smarty pants in order to win the love of a genius girl, Janet Nelson Jr. But later, the pants get a mind of their own.
Johnny sneaks into Lila's car along with Susan and Mary on Take Your Daughter to Work Day, thinking that it's unfair that girls don't have to go to school on this day, but boys do. When the kids get to Lila's workplace, they sneak into a lab and accidentally release a missile.
Johnny brings a toy, Nasteria, to life. But the toy decides to destroy Porkbelly. Now Johnny needs to stop the evil action figure with a toy force, led by Nasteria's arch enemy, Mega Roboticle.
Johnny steals a rocket his sisters made to travel to the moon so he can write his report. Unexpectedly, he battles some moon monsters and rescues Canadian astronauts.
Johnny uses a gadget to travel into a movie, The Quickest and the Monkiest. But what happens when the gadget gets stuck and the movie has a bad ending?
Johnny's sisters invent a time rewinder that can go back up to 5 minutes and they use it to get Johnny in trouble. Infuriated, he tries multiple times to steal this, but he fails; eventually, he gets a similar one from Bling-Bling Boy.
Johnny becomes Johnny X again in order to take down Bling-Bling's latest evil invention, Repto-Slicer.
Johnny and Dukey try Susan and Mary's ultimate scooter and are wanted in the future.
Susan and Mary put a device on Dukey, making him respond to their every command. Now Johnny must stop Susan and Mary, and get his best friend back.
Johnny uses a device to free everyone of zits.
Johnny and Dukey must help a pathetic pirate, Nobeard, take down his powerful brother pirate, Blackbeard, and impress his father, Greybeard. Johnny goes back to the future to get his sisters' help.
An evil toymaker named Wacko gives out robots to all the children of Porkbelly, which imprison them. The gang seeks assistance from the Turbo Toy Force.
Johnny starts his own channel over a channel which only broadcast emergencies and tests. Later, the army needs the channel for a runaway plane.
Eugene creates a device that turns himself, Johnny, and Dukey into young children, interfering with Johnny's video game showdown with Sissy.
Johnny makes a theme park called Johnnyland in the backyard. However, Hugh demands the park be torn down, later stumbling into an unstable ride with Lila.
Hugh's constant sayings of "no" begin to infuriate Johnny, so, with Susan and Mary's help, they make a new one. However, when the new dad gets exposed to the plutonium he got for Susan and Mary, things start to turn out ugly.
Johnny is trying to have the perfect Saturday, but Sissy ruins it by trying to practice William Tell archery on Johnny. Johnny then uses Susan and Mary's Saturday Repeater machine to try again.
Johnny, Dukey, and the sisters go to an ice cream factory, in order to get the recipe for mint chip ice cream which Johnny and Dukey can't stop eating.
Dukey gets jealous when Johnny takes Repto-Slicer to school for pet day and not him. However, this lands him into danger of becoming a TV star.
An accident in Eugene's lab leaves Johnny overweight like him. Johnny uses his weight to become a rapper and to get a video game that he wanted. However, karma is after him and ruins his experience.
Johnny and Dukey must rescue Susan from Bling-Bling Boy in the forms of Johnny X and Super Pooch. Little do they know she doesn't want to be rescued, as Bling-Bling Boy has taken her on a cruise bot with a swimming pool, movie theater, anti-gravity chamber, video arcade, and her favorite restaurants among other luxuries.
Johnny and Dukey catch rainy day boredom, and use one of the sisters' devices, thinking that it is an inter-dimensional travel machine, and go into a land known as Johnnia.
Johnny makes 100 robot clones in order to do his chores for him, but the clones become defective soon after.
Johnny brings Porkbelly's founders back to life in order to help with his report.
Johnny and Dukey shrink themselves, and end up in Mr. Black's stomach and brain to make him forget that the General told Mr. Black and Mr. White to spy on Susan and Mary to stop them from doing dangerous experiments.
Johnny and his family go on vacation to a dude ranch on Susan and Mary's choice, but it is invaded by an outlaw motorcycle club shortly after they arrive. With the help from Bling-Bling Boy and Gil, both whom have also been taken a trip to the ranch, the Tests resolve to stop the bikers from ruining their fun and take back their holiday.
Johnny goes to the Behemoth, the ultimate downhill ski resort. However, he has to find ways to go downhill since the ski captain doesn't let kids go.
It is a hot day and Johnny's family cannot seem to find a place where they can cool off and get wet. They go to Lake Pork-Ness, which is rumored to have a monster inhabitant. Susan and Mary believe that the idea is a total myth and try to prove there are no monsters in the lake.
Five evil villains who have been defeated previously by Johnny (Wacko, the Bee Keeper, Brain Freezer, Mr. Mittens and Albert the butler) team up and kidnap him. Now it's up to Susan, Mary, Dukey, Bling-Bling, Gil, and Bumper to save him.
Susan and Mary create Gil cyborgs to make Gil jealous but they try to eliminate Gil and anyone in their path. It's up to Johnny to stop them. Meanwhile, the girls keep Gil "safe" in a box in their lab.