Suggestions by @parkerc

Doug Jones

as Zeta Reticulans in Public Domain

Ethan Hawke

as The Green Knight in Public Domain

Ralph Ineson

as The Green Knight in Public Domain

Adam Scherr

as Giant of Saint Michael's Mount in Public Domain

Viggo Mortensen

as Centaurus the Centaur in Public Domain

Fetty Wap

as Cyclops in Public Domain

Omos

as Asterion the Minotaur in Public Domain

Cara Delevingne

as Morgana in Public Domain

Jon Hamm

as Thomas Angelo in Mafia (TV Show)

Conor McGregor

as Ireland in UFC Olympics

Jason Statham

as England in UFC Olympics

Idris Elba

as England in UFC Olympics

Chris Evans

as United States of America in UFC Olympics

Jai Courtney

as Australia in UFC Olympics

Chris Hemsworth

as Australia in UFC Olympics

Hugh Jackman

as Australia in UFC Olympics

Keanu Reeves

as Canada in UFC Olympics

Ryan Gosling

as Canada in UFC Olympics

Ryan Reynolds

as Canada in UFC Olympics

Georges St-Pierre

as Canada in UFC Olympics