Jay: british/irish

Kai: japanese

Nya: japanese

Cole: spanish/porteguese

Zane: russian

Lloyd: chinese/american

Wu: chinese

Misako: chinese

Garmadon: american (tho his father and brother are chinese XD)

Morro: japanese

Ronin: american (US)

Dareth: british

Skylor: swedish

Seliel: indian/american

Cyrus borg: japanese/american

Pixal: japanese/american

Chen: chinese

Delara: italian

Flintlock: british

Doubloon: italian

Chamille: french

Toxikita: canadian

Ash: german

Shade: romanian

Carloff: brazilian

Neuro: danish

Paleman: french

Turner: australian

Bolobo: african

Gravis: indian

Jacob: american (US)

Ed: british

Edna: irish

Ray: japanese

Maya: japanese

Dr.Julien: russian

Lou: spanish

Dr.Saunders: belgian

Nelson: dutch

Mailman: philippine

Captain Soto: greek

First spinjitsu master: chinese

Rufus MacAllister: canadian

The old commissioner: german

The prison manager: american (US)

Tommy (detective): polish

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I couldn't think of more characters, that's all what I could came up with

Rufus MacAllister is the comic writer at the 'mother doomsday' where lloyd takes the ninja in ep 18 'child's play'