Suggestions by @sonictiger

Natalia Dyer

as Young Marlena in Clover

Cloverfield Monster

as Clover in Clover

Gyaos

as Gyaos in Gamera

Gamera

as Gamera in Gamera

Edward Norton

as William Stenz in Godzilla: World Destroyer

Jeffrey Wright

as Director Guillerman in Godzilla: World Destroyer

Kyle Chandler

as Mark Russell in Godzilla: World Destroyer

Noah Schnapp

as Sam Brody in Godzilla: World Destroyer

Millie Bobby Brown

as Madison Russell in Godzilla: World Destroyer

Destroyah

as Destroyah in Godzilla: World Destroyer

Godzilla (Monsterverse)

as Godzilla in Godzilla: World Destroyer

Varan

as Varan in Rodan

Rodan (Radon)

as Rodan in Rodan

Battra

as Battra in Mothra: Queen of The Monsters

Mothra (Mosura)

as Mothra in Mothra: Queen of The Monsters

Claudia Kim

as Ling Chen in Mothra: Queen of The Monsters

Zhang Ziyi

as Ilene Chen in Mothra: Queen of The Monsters

Warbat

as Warbat in King Kong

Gorosaurus

as Gorosaurus in King Kong

Joe Morton

as Houston Brooks in King Kong