Screen legend Julie Andrews is storming movie theaters this Christmas, but it won’t be alongside Emily Blunt on Cherry Tree Lane.

Curiously, Andrews will voice a key role in “Aquaman,’ the franchise hopeful from DC Films and Warner Bros. lead by Jason Momoa.

The “Sound of Music” star will voice Karathen, a mythical sea creature that helps Momoa’s waterbound hero broker peace between Atlantis and the dry land, an individual familiar with the project told Variety.

“Aquaman” opens on Dec. 21, two days before the release of “Mary Poppins Returns,” when Blunt will take on a role originated by Andrews in the 1964 Disney classic (for which she won the Best Actress Oscar).

The news was first reported by Entertainment Weekly.

“We wanted the Karathen to have the voice of a classic British actress, albeit somewhat digitally altered,” Peter Safran, a producer on “Aquaman,” told the magazine.

“And when we found out Julie was interested and available and excited to do it, casting her was a no-brainer,” he said.

Andrews has steadily booked voice work in recent years, in animated blockbusters series like “Shrek” and “Despicable Me.” She has not appeared on screen since the 2010 family comedy “Tooth Fairy” with Dwayne Johnson.

Andrews is repped by WME and management company Media Four.