The 66-year-old actress' voice features throughout the animated movie, the sequel to 2003's Finding Nemo. She plays herself, and her dulcet tones pop up at various times during the film, such as when she welcomes the fish to the Marine Life Institute.

Director Andrew Stanton had the idea of asking Sigourney to be involved in the film, and is thrilled she agreed to what he believes is a "winning" concept.

"It was just funny to us," Andrew laughed in an interview with Slash Film. "I mean she’s the voice of The Blue Planet series if you buy the American or North American versions of that series. She’s also done other nature conservations. She’s big with stuff that she experienced from Gorillas in the Mist. But she’s also the voice of the planetarium show at the Academy of Sciences in San Francisco. So she was the equivalent of David Attenborough to me for nature.

"So I thought, 'Wouldn’t be funny if she did the voice?' And because we know her, we thought, 'This will be a nice card to pull. It’d be hilarious if she plays herself.' I waited till the last minute to ask her because we were worried it’d get cut, maybe it wouldn’t work in previews," he added. "So it was a scratch voice till the bitter end, and then thank goodness she said yes, because I think it’s such a winning idea."

Andrew also teased that Pixar fans should look out for a reference to the upcoming Cars 3 in Finding Dory. It's something directors often do ahead of the next Pixar release, but it isn't an obvious reference.

"There is a Cars 3 reference somewhere else. But it’s not a literal car," he smiled. "That’s the biggest hint I’ll give you. It’s not a literal car in the film."