Dennis, his dog Gnasher and their friends JJ, Rubi and Pieface get into trouble at Bash Street School and around Beanotown, often breaking rules and causing problems for Walter.
The kids of Beanotown decide that they can run the town far better than the grown-ups; the adults accept the challenge, but what seems like a dream come true, isn't nearly as easy or fun as they'd hoped.
On the first day of a new school year, Dennis and the gang imagine all the things that might be new and unfamiliar at Bash Street School; by the time they reach the front gates, they're all expecting the worst.
An order mix-up leads to a delivery of hyperactive tentacles at Bash Street School; no one wants the duty of looking after the pesky things, and attempts to duck out of the tentacle-care duties lead to chaos.
There's a new tripe hound in Beanotown, and Gnasher falls head over paws in love with her; Bertie's looking after the visiting dog, Ginger, and determined to keep her away from riff-raff like Gnasher.
Dennis is excited to trial a pair of high-tech Smarty Pants - underpants with all the capabilities of a smartphone; but whenever he and the gang test the pants, Walter's always one step ahead of them.
Dennis can't get Grizzly's new animal training method to work on wilful Gnasher; but when they realize that Gnasher can use the method to get humans to obey him instead, they exploit this new power to the max.
Dennis and the gang convince Mrs. Creecher that Monday is actually Sunday, in the hope of extending their weekend.
It's Pieface's turn to look after the class hamster, Space Captain Harrison McScruff-Butt; his own self-doubt and Walter's resolve to sabotage him lead to a rescue mission to free Scruff-Butt from Walter's mansion.
Miss Mistry arranges to tag along with Dennis and the gang after school, in an attempt to enhance her teaching skills, and prevent School Governor Pfooflepfeffer from banning her beloved teaching magazine.
Determined to prove he can accomplish a task without getting distracted, Dennis takes on the simple job of bringing the class register to the school office; he instantly distracts himself on an epic scale.
Dennis was up most of the night and can barely stay awake; Gnasher and the gang work hard to help steer dozing Dennis through the day, when all he wants to do is continue to dream about battling Zombie-Spiders.
A classmate who Dennis and Walter barely know is appointed as class 3C's Late Monitor; the boys find a way to cozy up with him.
Whilst helping Sergeant Slipper prove that he has what it takes to remain Beanotown's policeman, the gang unknowingly become entangled in Doctor Pfooflepfeffer's real theft.
Dennis dresses Gnasher up as a rare breed of animal which he says is nesting in Bash Street School - hoping to get the school shut down on the day of a daunting and difficult test.
Gnasher is practically immobile inside a full-body cast; when he goes missing, Dennis and the gang race all over Beanotown to find him, always one step behind the helpless hound.
The gang find out that JJ has a set of pre-match good-luck rituals; in the run-up to an important Blamjitsu event, Walter deviously throws bad-luck omens into JJ's path, threatening her chances of success.
Walter and Dennis go head-to-head in a sponsored silence; being quiet doesn't come naturally to either of them, as they struggle to make it through a chaotic school day and keep schtum.
Dennis leads the gang on the baffling trail of a mysterious Beanotown secret society.
When Dennis thinks Gnasher has trashed a valuable piece of hideous art, the gang try desperately to cover up the damage and produce a decoy that's as convincingly terrible as the original.
Dennis and Gnasher want to put their hands in a patch of wet cement, but Sergeant Slipper is determined to not let that happen.
Rubi's dance-machine invention gets accidentally muddled up with Crusty the Robot Pie's coding; Dennis and Gnasher have to dance on it all day in perfect sync, or Crusty's entire persona will be wiped forever.
Dennis and the gang take on the power of WilburCorp to stop Walter's new line of collectable toys ruining the Beanotown environment with wasteful plastic packaging.
JJ applies for an elite sporting school; not realizing it's hosted miles away from Beanotown, JJ needs to do badly in the sporting assessment to get out of it, but losing doesn't come naturally to JJ.
Professor von Screwtop gets mistaken for the new kid in school, and joins Class 3C for the day; Rubi gets so embarrassed at her dad's antics that she resorts to pranking to get him into trouble and out of the way.
When Olive surprises herself and everyone around her by actually becoming a good cook, Dr. Pfooflepfeffer tries to cash in by turning the school canteen into an exclusive and super-expensive dining experience.
In the run-up to the school play, spooky incidents around the school make the gang wonder if the mythical Bash Street Bogeyman might be real, and still stalking the corridors.
Miss Mistry and Mrs. Creecher clash over the best way to teach Class 3C about butterflies; the gang just wants to get through the lesson so they can get out of school in time for a Grizzly Griller Wildlife Event.
Deep in the caverns below Beanotown town hall, a mysterious species of oversized hamsters may or may not exist, so they could be at risk of being hunted down and turned into fluffy slippers.
The gang produce a hand-drawn comic, which is a surprise hit all around Beanotown; envious of their success, Walter embarks on a mission of cartoon-drawing sabotage.
Tricked into a townwide cleanup, Dennis and Walter are paired up against their wills; when their bickering leads them off course, they're forced to cooperate to survive in the wilderness of Beanotown Woods.
Dennis and Gnasher accidentally do good deeds for the people of Beanotown; intrigued by the new sensation of being thanked and appreciated, they go on a helping rampage and leave a wake of mayhem behind them.
Dennis and his friends rebel against an outbreak of unfair fun-killing rules that are being imposed on Beanotown.
Dennis and the gang can't wait for their all-day PE training day with Grizzly Griller, and are baffled when their idol makes them learn a range of naff boring non-sports that only Walter excels at.
Dennis is on his last warning, one more prank in school, and he'll be sent to Grim Lane School; while he struggles to sustain a prank-less day, Walter conspires to make Dennis fail and get thrown out of school.
Dennis doesn't realize the pressure he's putting on Rubi to excel in the school science fair is giving her a severe case of inventor's block.
Dennis is accidentally elected Class President and is eager to shed the burden that comes with the title; but every daft class policy he declares, only makes him a more popular presidential choice than before.
In a somewhat misguided attempt to resolve Dennis and Walter's spiraling competitiveness, Miss Mistry offers thumb wrestling as a solution.
Doctor Pfooflepfeffer's first act as Head of Governors is to turn Bash Street School into a boarding school; Duped into being held at school indefinitely, the pupils devise a series of daring attempts to escape.
Walter's pampered cat Clawdia persuades her way into the gang, and only Gnasher can tell that she's got a hidden agenda to oust him from Dennis' life forever.
The gangs enter Pieface into a comedy contest to make him realize how brilliantly funny he is; determined to win the crown, Walter uses the latest WilburCorp gadget on the unsuspecting audience to sway the vote.
Torn between practising Blamjitsu with the yeti, and helping the Dinmakers write a new school song, JJ tries to combine the two by bringing the yeti along to band practice disguised as a very hairy roadie.
With all his mates unfairly kept inside at lunchtime by a cranky Mrs. Creecher, Dennis is exasperated to find that he can't land himself in detention, no matter how much he misbehaves.
Eager to prove her babysitting ability for a permit, Gran's on the hunt for a baby stand-in; Walter is suspiciously all too willing to offer up Bertie.
Paul the Potato is love-struck by the poster-girl potato advertising WilburCorp's new line of super-posh chips; the gang stage a daring potato-rescue in the WilburCorp factory.
With Paul on vacation, Pieface falls under the influence of a fiery chili pepper and unexpectedly turns rogue.
In an attempt to deprive Gnasher of the food that fuels his active gnashy ways, Walter takes over Butch Butcher's sausage-making business; his careless manufacturing produces a monster-sized fatberg under Beanotown.
Doctor Pfooflepfeffer covets the world-beating power of Gnasher's indestructible teeth; she'll stop at nothing to get her hands on one of those doggy-dental marvels.
Convinced that Mrs. Creecher is secretly a master of Blamjitsu, JJ persuades the gang to help her trick Mrs. Creecher into revealing her blam credentials.
The after-school art club comes under threat of imminent demolition; while trying to save the club, the gang end up on the trail of the mysterious undercover urban artist known only as Pranksy.
The time comes for Gnasher's annual bath, but the stinky hound will do anything to avoid the tub, leading to Dennis and Gnasher going head-to-head in a town-wide game of cat-and-mouse.
Pieface secretly does underpants-laundry chores for Walter, hoping to help Dennis save up some cash; he urges the gang to audition for a replacement Pieface to make up for his mysterious absence.
New teacher Miss Mistry takes Class 3C on a trip to Flumes 'o' Doom theme park, but if anyone arrives a nanosecond late, the bus leaves without them. Walter pulls out all the stops to make Dennis late for the bus.
