The wizarding world is crawling with creatures – some proud, some vindictive, some visible only to those who have witnessed death. They function as familiars, friends and foes. And some of them, it seems, are mainly there to mess with the nearest witch or wizard.

Nifflers

These cute little diggers are the original mischief-makers. Their affinity for anything expensive makes them more dangerous than Dementors (if you care more about your watch than your soul). It makes sense that they’re adorable; it makes it much more likely that you’ll forgive them for raiding your jewellery box, robbing you blind, and destroying your house.

The Nifflers dived in and out of the patch of earth as though it was water, each scurrying back to the student who had released it and spitting gold into their hands. Ron’s was particularly efficient; it had soon filled his lap with coins.

‘Can you buy these as pets, Hagrid?’ he asked excitedly, as his Niffler dived back into the soil, splattering his robes.

‘Yer mum wouldn’ be happy, Ron,’ said Hagrid, grinning, ‘they wreck houses, Nifflers.’
Harry Potter and the Goblet of Fire

Kreacher

House-elves as an entity aren’t exactly mischief-makers, interested as they are in serving – but the pages of Harry Potter are studded with diminutive tea-towel-clad rebels, and Kreacher is the most intent on causing trouble.

Alternately scattering Dungbombs, prowling after dark, and smuggling valuables in his loincloth, Kreacher’s deep love for his family resulted in plenty of problems for the new occupants of his domain.

There was the sound of pattering feet, a blaze of shining copper, an echoing clang and a shriek of agony: Kreacher had taken a run at Mundungus and hit him over the head with a saucepan.

‘Call ’im off, call ’im off, ’e should be locked up!’ screamed Mundungus, cowering as Kreacher raised the heavy-bottomed pan again.

‘Kreacher, no!’ shouted Harry.

Kreacher’s thin arms trembled with the weight of the pan, still held aloft.

‘Perhaps just one more, Master Harry, for luck?’
Harry Potter and Deathly Hallows

Hedwig

Hedwig is a loyal friend and a reliable mail carrier, but she’s also got plenty of personality, which more often than not expresses itself in the form of non-verbal jokes. She nibbles ears, nips wrists and disapproves of tropical birds. She’s often present when Harry receives bad or worrying news (because she brings it, tied to her leg) and if he overreacts, she makes sure he knows, by cuffing him about the head with her wing.

Hedwig came fluttering down onto his shoulder, and held out her leg.

‘I can’t use you,’ Harry told her, looking around for the school owls. ‘I’ve got to use one of these ...’

Hedwig gave a very loud hoot, and took off so suddenly that her talons cut into his shoulder. She kept her back to Harry all the time he was tying his letter to the leg of a large barn owl. When the barn owl had flown off, Harry reached out to stroke Hedwig, but she clicked her beak furiously and soared up into the rafters out of reach.

‘First Ron, then you,’ said Harry angrily. ‘This isn’t my fault.’
Harry Potter and the Prisoner of Azkaban

Grindylows

There are degrees of mischief, and Grindylows sit further towards the murderous end, given their predilection for dragging witches and wizards down to watery deaths. But they’re small! Green! Cute!

Harry twisted his body around and saw a Grindylow, a small, horned water demon, poking out of the weeds, its long fingers clutched tightly around Harry’s leg, its pointed fangs bared – Harry stuck his webbed hand quickly inside his robes and fumbled for his wand – by the time he had grasped it, two more Grindylows had risen out of the weed, had seized handfuls of Harry’s robes, and were attempting to drag him down.
Harry Potter and the Goblet of Fire

Nargles

The actual presence of Nargles is yet to be verified, but if Luna tells us that they infest mistletoe, then who are we to disbelieve her?

Freshly caught Cornish Pixies

Gilderoy Lockhart was always a great lover of a mischievous wink, so it’s no surprise that he brought these blue-hued wreckers of havoc into the classrooms of Hogwarts.

Shockingly strong and good at working in teams, it didn’t take long for a cage full of the cobalt sprites to reduce a Defence Against the Dark Arts class to panic.

It was pandemonium. The pixies shot in every direction like rockets. Two of them seized Neville by the ears and lifted him into the air. Several shot straight through the window, showering the back row with broken glass. The rest proceeded to wreck the classroom more effectively than a rampaging rhino. They grabbed ink bottles and sprayed the class with them, shredded books and papers, tore pictures from the walls, upended the waste bin, grabbed bags and books and threw them out of the smashed window; within minutes, half the class was sheltering under desks and Neville was swinging from the candelabra in the ceiling.
Harry Potter and the Chamber of Secrets