Suggestions by @harrypotterfan7

Leo Suter

as William Weasley in Harry Potter

Ferdia Walsh-Peelo

as William Weasley in Harry Potter

Fionn Whitehead

as Charles Weasley in Harry Potter

Alex Lawther

as Charles Weasley in Harry Potter

Ralph Fiennes

as Voldemort (present time in the book) in Harry Potter

Kelly Macdonald

as Helena Ravenclaw in Harry Potter

Simon Fisher-Becker

as Fat Friar (Hufflepuff ghost) in Harry Potter

An Unknown Child Actor

as Dudley Dursley in Harry Potter

Tom Hollander

as Rubeus Hagrid in Harry Potter

Michelle Fairley

as Professor Minerva McGonagall in Harry Potter

Alan Cumming

as Xenophilius Lovegood in Harry Potter

Mackenzie Crook

as Argus Filch in Harry Potter

Maisie Williams

as Merope Riddle (née Gaunt) in Harry Potter

Emily Perkins

as Merope Riddle (née Gaunt) in Harry Potter

Hannah Murray

as Merope Riddle (née Gaunt) in Harry Potter

George MacKay

as Morfin Gaunt in Harry Potter

Ben Hardy

as Morfin Gaunt in Harry Potter

Freddie Highmore

as Morfin Gaunt in Harry Potter

Will Poulter

as Morfin Gaunt in Harry Potter

Jeremy Irons

as Marvolo Gaunt in Harry Potter