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|“||Believe me, when Arendelle learns the truth about her, they shall side with me.||„|
|~ The Duke to Helga|
The Duke of Weselton from Frozen appears in live-action form in the seventh episode of the fourth season of Once Upon a Time. The flashbacks of the episode are set before the film.
During the King of Arendelle's 70th birthday celebration, the Duke of Weselton visits and becomes enamored with Helga, one of the three Arendelle princesses. Helga presents him to her father, and afterwards, the Duke shares a dance with her. When they begin a courtship, he comes across Helga's eldest sister, Ingrid, who is heir to the throne. After the Duke introduces himself, she moves to find Helga.
However, he stops Ingrid and remarks on her incredible beauty. As he makes advances on her, Ingrid rebuffs him, and out of panic, she blasts him away with ice magic. While he is sprawled on the ground, an unsuspecting Helga arrives. To cover up his failed seduction, the Duke explains to Helga that Ingrid attempted to win his romantic affection, but when he refused her, she used magic on him.
However plausible the lie is, an unamused Helga rejects him as she knows the kind of man he is. Enraged, the Duke threatens to expose Ingrid to everyone in Arendelle because he believes the people deserve to know their future queen is a monster. At this, an angered Ingrid attempts to blast him, but Helga intervenes and takes the magical hit while the Duke escapes.
Later, his mind is wiped out of the incident and of both sisters' existence due to Grand Pabbie, who casts a memory spell on behalf of Gerda, the only remaining princess and heir to the throne following Ingrid's imprisonment.