Suggestions by @joshparker

Joseph Marcell

as Arch-Astronomer in The Colour of Magic

Benedict Wong

as Dactylos in The Colour of Magic

Matt Berry

as Mad Lord Snapcase in The Colour of Magic

Toby Jones

as Tethis in The Colour of Magic

Michael Gambon

as Griecha the First in The Colour of Magic

Taylor James

as Hrun in The Colour of Magic

Karen Gillan

as Liessa Dragon Lady in The Colour of Magic

Anthony Stewart Head

as Fate in The Colour of Magic

Gugu Mbatha-Raw

as The Lady in The Colour of Magic

Benedict Cumberbatch

as Death in The Colour of Magic

Masi Oka

as Twoflower in The Colour of Magic

Mackenzie Crook

as Rincewind in The Colour of Magic

Anya Taylor-Joy

as Susan Sto-Helit in Discworld

Kate Dickie

as Granny Weatherwax in Discworld

Benedict Cumberbatch

as Death in Discworld

Mackenzie Crook

as Rincewind in Discworld

David Fierro

as Kasabian in Sandman Slim

Christopher Backus

as James Stark in Sandman Slim

Dakota Fanning

as Voice of Pinhead in The Hellbound Heart

Adam Pearson

as Lead Cenobite in The Hellbound Heart