Isla Fisher's director wanted her 'Rango' character to sound like a mix of Clint Eastwood and Holly Hunter.
The actress lends her voice to desert iguana Beans in the animated movie and revealed she watched a collection of old western movies to get the unusual inflections director Gore Verbinski requested.
She explained: "Gore already had the idea of the voice and then I joined. He wanted her to sound like Holly Hunter and a little bit like Clint Eastwood so I actually watched 'Raising Arizona' a bunch of times and just kept practicing until the pitch was nice and low and I watched, of course, a bunch of old Westerns.
"I didn't really know the genre - growing up in Australia it wasn't a big deal. So for me it was really exciting to see those amazing old movies."
However, Gore has credited Isla with developing the character even further, citing her "neurotic sense of humour" as vital.
He told BANG Showbiz: "The accents are only a part of it, I mean she brought her own neurotic sense of humour, which is kind of more important."