But it turns out one of its cheekiest moments was improvised.

It was added by actress Yvonne Wilder, then credited as Yvonne Othon.

“I did the play in London with Yvonne so I knew her before the movie.

WEST SIDE STORY

Rita Moreno in ‘West Side Story’.Everett Collection

But Yvonne’s humor was adopted by all of us.”

For all three original cast members, “America” remains a personal favorite.

“I simply adore watching ‘America,'” said Moreno.

“Not only for my part of the dance, but I adore watching George.

He is just so bloody elegant; he’s just a super, very unusual dancer.

He has that Astaire thing about him.

I love watching it.

I love me in it; I think I’m funny.”

“I had to do my best acting to hate him…

When the movie finished, George and I became great, great friends.”

“I’m really grateful for this movie and to be identified with it,” Chakiris said.

It’s a real blessing."

Watch the clip above for more.