Kristen Bell made six-year-old Avery's day after she left her a voicemail in the voice of hercharacter Anna. Avery, who was diagnosed with diffuse intrinsic pontine glioma, an inoperable brain tumor, last month, is seen beaming as she listens to the heart-warming message from her favourite Disney princess.

Kristen Bell at the premiere in Los Angeles in 2013

"Hi Avery! This is Princess Anna of Arendelle," says Kristen, in character. "I just wanted to call and say hello. So, hello! I hope you're having a great day and playing a lot with Hoppy Jumpy. I love bunnies!"

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The video, which has since garnered over 979,000 views, sees little Avery looking adorably excited as she hears from her heroine, who has some extra special news for the brave little girl.

"What's that, Elsa?" continues Kristen, referencing the hit animated feature's other protagonist. "Wow, okay, I'll tell her! Um, Avery my sister Elsa says she's heard that you've been such a good girl and that you've been so brave that she has decided to crown you as an honorary princess of Arendelle! Wow! That's so exciting! I think you'll make a great princess."

Kristen voiced character Anna (left) in Disney's animated hit

Inspired by Hans Christian Anderson’s , follows Anna, voiced by Kristen, a princess who sets off to find her estranged sister, Elsa, voiced by Idina Menzel, whose ability to turn anything she touches to ice has trapped the kingdom in an eternal winter.

Released in 2013, the film grossed over a billion dollars at the box office, making it the highest-grossing animated film of all time – so fans were delighted but not surprised when Disney confirmed in March that a full-length sequel was in the works.

Speaking at the Walt Disney Company's shareholders meeting on Thursday, John Lasseter said: "We enjoyed making so much and being back in that world with those characters.

"[Directors] Jennifer Lee and Chris Buck have come up with a great idea for a sequel and you will be hearing a lot more about it and we’re taking you back to Arendelle. We are so excited about that."

Kristen also expressed her excitement at the time, taking to Twitter to share the good news. "Dreams really do come 2!!! #FROZEN2 #itsofficial", she wrote to her followers, along with a humorous picture of herself sleeping on a bag of ice.

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