Suggestions by @mischief

Kaya Scodelario

as Ariana Dumbledore in The Young Dumbledore

Lily Collins

as Sirius Black in Genderbent Marauders

Gal Gadot

as Sirius Black in Genderbent Marauders

Claudia Kim

as Nagini in RIDDLE

Simon Pegg

as Armando Dippet in RIDDLE

Elizabeth Gillies

as Dolores Umbridge in RIDDLE

Kristen Stewart

as Rolanda Hooch in RIDDLE

Tom Holland

as Florean Fortescue in RIDDLE

Jacob Elordi

as Hans in Frozen

Alexandra Daddario

as Petunia Evans in The Marauders

Elizabeth Gillies

as Megara in Fairytales

Zayn Malik

as Aladdin in Fairytales

Elle Fanning

as Alice in Fairytales

Kiernan Shipka

as Tinker Bell in Fairytales

Adam Driver

as Severus Snape in The Marauders

Eiza González

as Petunia Evans in The Marauders

Amybeth McNulty

as Molly Prewett in The Marauders

Tom Holland

as Arthur Weasley in The Marauders

Louis Hofmann

as Xenophilius Lovegood in The Marauders

Elle Fanning

as Pandora MacMillan in The Marauders