Young Ingrid is played by Brighton Sharbino, best known as Lizzie Samuels on The Walking Dead. Definitely looks like a young Elizabeth Mitchell:
Ava Marie Telek as Young Gerda:
There are no photos of Bailey Herbert, who plays Young Helga.
Jonathan Runyon as Duke. Please don’t tell me we’re going to see a young Duke of Weselton? He’s pretty much the only Frozen character who hasn’t appeared, aside from Olaf:
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