Hmm let's see:
--Dursleys are child beaters and are deliberately molded this way so evil-Dumbles gets a trusting pawn-Harry
--Potter is somehow super-rich but doesn't know it
--magical trunks which turn into small houses on the inside, including potions lab and library ... standard equip for the newHarry! (TM) or self-insert
--students in houses other than Gryfindor have different arrangements, usually single rooms in Slytherin, or house library surpassing school library in Ravenclaw
--Weasley twin created diabolical plans always work
--Wizarding World is super ignorant of modernization, to the point where modern writing utensils, television, and cars are muggle curiosities (this has an Arthur Weasley basis in books, but fanon takes it to the extreme)
--alternatively, any wizard who combines modern technology with magic can easily dominate the wizarding world, ignoring why generations of muggle-borns have not done this
--everyone powerful is an animagus
--parseltongue is so super-unique it has a dark-magic-haxx sub-branch known as 'parselmagic'
--ministry is corrupt and/or stupid, often beyond absurdity
--Dementors can't die, of if they can die are ridiculously hard to kill... often SuperHarry! proves he is super with Dementor destruction
--House Elf magic can be taught to wizards, or is in general superior to normal Wizarding magic (usually for teleportation, have also seen for food conjuration and spying through wards)
--any canon relationship the author doesn't like is from a love potion
--male veela, the standard plot vehicle for harems
--any plot inconsistency in the fic can be explained via a memory charm
--the Veil in the Department of Mysteries leads to whatever alternate world the author wants to do as a crossover
--Dursleys are child beaters and are deliberately molded this way so evil-Dumbles gets a trusting pawn-Harry
--Potter is somehow super-rich but doesn't know it
--magical trunks which turn into small houses on the inside, including potions lab and library ... standard equip for the newHarry! (TM) or self-insert
--students in houses other than Gryfindor have different arrangements, usually single rooms in Slytherin, or house library surpassing school library in Ravenclaw
--Weasley twin created diabolical plans always work
--Wizarding World is super ignorant of modernization, to the point where modern writing utensils, television, and cars are muggle curiosities (this has an Arthur Weasley basis in books, but fanon takes it to the extreme)
--alternatively, any wizard who combines modern technology with magic can easily dominate the wizarding world, ignoring why generations of muggle-borns have not done this
--everyone powerful is an animagus
--parseltongue is so super-unique it has a dark-magic-haxx sub-branch known as 'parselmagic'
--ministry is corrupt and/or stupid, often beyond absurdity
--Dementors can't die, of if they can die are ridiculously hard to kill... often SuperHarry! proves he is super with Dementor destruction
--House Elf magic can be taught to wizards, or is in general superior to normal Wizarding magic (usually for teleportation, have also seen for food conjuration and spying through wards)
--any canon relationship the author doesn't like is from a love potion
--male veela, the standard plot vehicle for harems
--any plot inconsistency in the fic can be explained via a memory charm
--the Veil in the Department of Mysteries leads to whatever alternate world the author wants to do as a crossover