The first and second series of the television show Round the Twist were written by Paul Jennings and based on his published short stories; episodes after this point were original stories written by other people. The lesser-known series Driven Crazy was likewise based on his previously unadapted stories.
Co-authored two series with Morris Gleitzman: Wicked! and Deadly!.
His work is often quirky in style, often drawing upon weird, spooky and fantastical occurrences, including liberal amounts of gross-out humour and Nightmare Fuel. For these last reasons especially, Moral Guardians have frequently questioned the appropriateness of his work for younger readers. For much the same reasons, these younger readers have often loved it.
Jennings' work provides examples of:
- Ambiguous Gender: Star, the horse in Spaghetti Pig-Out.
- And, in earlier prints, Beethoven, the budgie in Only Gilt, and Ohda, the dog in Smelly Feat.
- Anyone Can Die: Don't ever presume an individaul is safe from death just because of traits like their age or species; he'll happily kill off kids and pets.
- Be Careful What You Wish For: His favourite Aesop is you should always consider if you really, ''really' want what you think you want.
- Big Brother Bully: The main character of Inside Out; the brothers of the main characters of The Velvet Throne and Ringing Wet.
- Body Horror: The main characters of Burp and Nails, amongst others; the former bloats up until he becomes so morbidly obese that his heart can't take the strain and he dies, his final words being a loud belch, whilst the latter has finger and toenails sprout all over his hands, feet, arms and legs until it turns out they're actually scales and he's turning into a merman. Clear As Mud uses it twice.
- Body to Jewel: The main character of Tonsil Eye 'Tis grows a third eye on his finger that cries tears that grow into garden gnomes. In the end, he starts a business selling them.
- Cloning Blues: The Copy.
- Ambiguous Clone Ending: Played With - The Copy has the same memories as the main character, and becomes convinced that he is the original, and that "The Copy" is trying to live his life. It soon turns out the story from after the boy uses the copy machine and passes out is told using the clone's memories instead of the original's, and the original boy is dead.
- Expendable Clone
- Clothes Make the Maniac: The acrobat's outfit in Know All, where the scarecrow becomes evil when it wears the acrobat's outfit, because it belonged to an evil person. The other circus clothes do similar things, with Matthew fooling when he dresses in the clown's costume then throwing knives perfectly when he wears the knife thrower's costume. Kate uses this at the end by wearing the fortune teller's costume.
- Downer Ending: Many stories end in depressing or morbid fates for the narrator.
- Failed Attempt at Scaring: In Inside Out, a horror film buff goes to the local Haunted House and finds himself incredibly bored by all the horrifying phenomena he witnesses. Unfortunately, the ghost haunting the place is trying to pass an exam, and if he can't scare the protagonist in the allotted time, the ghost will have to retake the exam - leaving said protagonist trapped until he can be used as a victim all over again next semester. So, the protagonist does his best to look scared at the ensuing display of fearsome gimmicks, even though he's Seen It All. What actually works is the ghost demonstrating a talent for magically turning objects inside-out, and then gearing up to use it on the protagonist. The examiner gives the ghost a passing grade and the protagonist is allowed to go free... but is left scared of everything as a result of his experiences.
- Great Accomplishment, Weak Credibility: The narrator of Smart Ice Cream is a Child Prodigy and an Insufferable Genius who is usually the only one in his class to get full marks in math. So when his classmate Dadien also gets full marks, the protagonist, who believes all his classmates are dumb, thinks Dadien must have cheated.
- Hoist by His Own Petard:
"He screamed all the way down."
- In one story, the Jerkass narrator is a know-it-all bully who regularly taunts and teases people while scoring high on tests. Over the course of the story, the people who he taunts and teases receive free ice cream from a mysterious ice cream man, and subsequently lose the trait he was teasing them about (e.g. a pimply-faced character's acne disappears overnight). Infuriated that he doesn't get any ice cream, he breaks into the man's truck at night and puts sand in every tub but the one labeled "Smart Ice Cream - for smart alecks" which he helps himself to. The final part of the story is riddled with spelling and grammatical errors, as the narrator wonders what happened... and can't work out whether one plus one is "free or for?"
- Also, the Gizmos in the Gizmo series wouldn't have caused so much trouble if the characters had just left them alone in the first place.
- The main character of The Strap-Box Flyer sells a miracle glue that holds anything together... for four hours, at which point it falls apart. He never tells anyone of this limitation, leading to a trail of sorrows from the destruction of prized belongings to a child drowning. He runs into a man who invented the strap-box flyer, which lets you fly. As they fly towards the clouds, all sense of time lost, the inventor casually reveals the conman's flyer is held together with his glue, and just then it falls apart.
- In No Is Yes, Dr Scrape has isolated his daughter, Linda, and spoken in a way that has taught her all the wrong words to everything. When their house catches fire and he is trapped inside, a fireman asks her if anyone is in there. She replies "No", because she thinks that no means yes. Her father has literally killed himself because his daughter lacks the knowledge to communicate with others. It is suggested that she began to understand that she had been taught the wrong words and may have left her father to die on purpose, but from Linda's earlier behaviour, it is more likely she still thought "no" meant "yes".
- Hurricane of Puns: His joint books with Ted Greenwood and Terry Denton, Spooner Or Later and Freeze A Crowd.
- Jerkass: One will always show up in his stories, usually as an antagonist, rarely as a protagonist. In the Gizmo books, the protagonist typically does something wrong for the approval of this kind of character.
- Karmic Death: The abovementioned Villain Protagonist of The Strap-Box Flyer, whose lies lead to a death during the course of the story — a boy he sells his glue to drowns after his broken canoe falls apart again when the glue wears off while he's sailing it — and are implied to have caused similar deaths in the past.
- Karmic Transformation: The seemingly fearless Big Brother Bully narrator of "Inside Out" is scornful toward and inconsiderate of his easily-scared sister. Wandering into an abandoned house at night, he is compelled to be the subject of a ghost's spooking exam, which the ghost passes by magically turning various objects inside out and then almost doing the same to the narrator, causing him to faint. He escapes physically unharmed but has lost his fearlessness and become even more timid than his sister; he now jumps at every sound and describes the Muppet movie she is watching as "really creepy".
- Magic A Is Magic A: His Twist Endings frequently follow logically from a previously established trait or truth of the work.
- Men Are Better Than Women: Played with in What A Woman. Sally is the only girl in her whole school and all the boys make fun of her because she comes last in all the Mini-Olympics events. Sally eventually proves them wrong when her athletic aunt's paperweight/trick box brings her good luck in both sports and other unrelated things. Eventually, the box is opened and all the boys faint to find her aunt's toe inside, while Sally doesn't. This is especially important since Sally's main tormentor has mentioned twice that only girls faint, so he proves that men are actually more faint-hearted than women.
- Mooning: The story Moonies revolves around the protagonist being forced by a bully to flash his naked butt at people driving along a road. He manages to get even by getting the bully to do the same... after the protagonist has drawn a very recognizable caricature of the bully's face on his arse, so the teacher he's mooning instantly realizes who it is.
- Naked People Are Funny: A lot of stories involve the characters being caught naked in public e.g. The Gizmo, Wunderpants and Pubic Hare.
- Our Mermaids Are Different: In Nails, mermen and mermaids can crossbreed with humans, with said offspring looking human until puberty, when they will start to grow what look like extra fingernails (really fish scales) up their fingers and eventually over various parts of their body, shortly before their legs fuse together to become the iconic tails.
- Picky People Eater: The Slobberers from the series Wicked! only eat flesh, bones and organs, not skin or hair. So their victims are left as hollowed out, dessicated skins when the Slobberers are done with them.
- Scary Scarecrows: Know All features a scarecrow come to life when it wears an acrobat costume due to a circus curse. The protagonist recognizes that the costume belonged to someone bad, and the costume passes on the person's evil.
- Teasing Parent: In the short story "A Mouthful", the protagonist's father loves to play pranks on his daughter and her friends. He's put too much pepper on their dinner, short-sheeted the beds, etc, but his favourite prank was to put fake cat poop on the table and pretend to eat it. The girl then tricks him into eating real cat food.
- Tomato Surprise and Tomato in the Mirror: A number of his stories, but notably The Copy.
- Tongue on the Flagpole: The story Ice Maiden features a boy kissing an ice sculpture and getting stuck.
- Toothy Bird: Picked Bones has two birds with teeth given to a child, with a warning to keep them away from his cat. He assumes it's because the cat will harm the birds. It turns out that this is not the case.
- Universal Remote Control: In the story "Spaghetti Pig-Out", a boy gets a remote that looks like a green chocolate bar that can control not only the VCR but people, flies, and cats.
- Verbal Tic: Without a Shirt is about a boy who can't help adding the titular phrase to everything he says without a shirt."You know I can't stop saying 'without a shirt' without a shirt."
- Weaponized Stench: In Smelly Feat, a boy saves a sea turtle from being slaughtered by using his feet that he didn't wash for months to scare away the bully that was going to kill her as she laid her eggs.
- Widget Series: His stories can more or less be considered weird Australian things.
- Wipe That Smile Off Your Face: The last line of Santa Claws is, "I wish you didn't have such a big mouth."
- You Can't Fight Fate: Looking into the eye of a Seeshell lets you see the future, and everything you see will happen — however, you can also manipulate fate to create a Self-Fulfilling Prophecy.