Suggestions by @mischief

Joshua Bassett

as Aberforth Dumbledore in The Young Dumbledore

Jeni Ross

as Muriel in The Young Dumbledore

Daisy Ridley

as Honoria in The Young Dumbledore

Natalia Dyer

as Honoria in The Young Dumbledore

Rebecca Ferguson

as Bathilda Bagshot in The Young Dumbledore

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