Sandra Bullock on How Brad Pitt Came to Have a Cameo in 'The Lost City' (Exclusive)

etonline.com:

 has a star-studded cast, and its cameos aren't too shabby either. ET's Rachel Smith spoke with Sandra Bullock at a special screening of the film in New York City on Monday, where she shared how Brad Pitt's part in the film came to be.«I honestly don't know Brad that well, we just keep doing each other favors.

And we don't really know each other,» Bullock said of Pitt, who plays a CIA operative in the film.The two are also starring in another action-adventure film together, , due out in July.«We just keep-- I think we were probably past life friends or something,» she went on to say of their work partnership turned friendship. «I just, for some reason, he asks for help, I show up.

I ask for help, he shows up. Maybe [a] mutual respect club, I don't know.»Bullock stars in the film as Loretta Sage, a reclusive romance-adventure author who's spent her career writing about exotic places.

Channing Tatum is the novels' cover model, Alan, who strives to embody the books' hero character, Dash, in real life.While the pair is promoting Loretta's latest book, she's kidnapped by an eccentric billionaire (Daniel Radcliffe), who wants to find the treasure featured in her newest novel.