Claire Danes was left disappointed on the set of her latest film because her unicorn's horn kept falling off.

The "Romeo and Juliet" actress is starring in the new fantasy movie "Stardust," in which her character is rescued by a unicorn, but the mythical beast didn't quite live up to her expectations.

Claire told the New York Daily News newspaper: "The horn kept falling off. I was so ecstatic to fulfill my six-year-old's fantasy and ride a goddamn unicorn! And when I mounted it, the horn fell off!"

The film - directed by Claudia Schiffer's husband Matthew Vaughn - also stars Robert De Niro, who plays a flying pirate who wears a corset and even does the cancan in one scene.

Vaughn admits the legendary actor was confused about his character's sexuality.

The filmmaker said: "Whenever Bob had any gay questions, I just said, 'What do you think, Bob?' He asked me, 'Am I gay or am I transsexual?' I told him 'Any kind of pirate you want to be, Bob.' "

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