Eva Longoria on mastering Castilian Spanish, working with Carmen Maura on 'Land of Women'

Since when is Castilian Spanish a dialect.

Castilian Spanish, often referred to simply as Castilian, is not a dialect but rather a standard form of the Spanish language. It is the variety of Spanish spoken in the region of Castile in Spain, and it serves as the basis for the standardized Spanish language used in Spain and much of Latin America. 

While there are many regional dialects within Spain (such as Andalusian, and others) and different varieties of Spanish spoken throughout the world, Castilian Spanish is considered the standard or normative form of the language, especially in formal contexts, media, and education.

"Castillian Spanish" as in "Mexican Spanish", "Argentinian Spanish" or "Panama Spanish"???...

hmmm seems to me someone does not know what is the "Spanish" language at all....

We started watching "Land of Women" but cut it before the end of the first episode.

didn’t castilian spanish come from people copying the lisp of the king/queen (?) so he or she would not feel embarrassed?

Longoria’s first bilingual television part included another challenge: interchangeably acting in English and Castilian Spanish, a dialect spoken in northern and central Spain.

“I was like, ‘I’ve never acted in Spanish. I’d like to do that,’” said Longoria. “If I’m going to go back on TV, I want it to be with something special and so it was worth all the effort of learning Castilian Spanish.”

The Mexican American actor said she didn’t grow up speaking Spanish but is familiar with Mexican Spanish thanks to her husband and the time they’ve spent living in Mexico City. Taking on Castilian Spanish was another challenge for the actor.

“I was just like my brain hurt at the end of the days. But it was a joy. I love exploring new characters through language or through accents,” she said.

Many actors simply 'play themselves', the same old arrogant egomaniacs that they are in real life.

But there are exceptions. Good actors can learn different accents or even languages and that truly is working, folks. That's using your head. And in such movies, they often hire dialect or language coaches to help them in their work.

For instance, a Native American actor in the epic 'Dances with Wolves' had to learn some Sioux because his Native language is Iroquois. Big difference. In the movie credits of 'Lethal Weapon 2' there is listed at least one 'dialect coach' for the actors who spoke South African dialects in their roles. That's what good acting is about, being flexible.