Blowing Smoke Up Her Ass (Expression) To give a gratuitous and insincere compliment. 

For reasons that make absolutely no sense to me, Maggie Gyllenhaal actually sought Katie Holmes approval before taking over the Rachel Dawes character in Christopher Nolan's Batman franchise. In fact, she nearly turned down the part, until she was assured that Holmes was on board. Gyllenhaal said:

"I wanted to be sure, first of all, that I had her blessing. And I was assured that I did. I'm a big fan of hers, I think she was really great in the first movie. And yet I felt like it wouldn't have done anyone any good if I tried to imitate her. Really what I decided was that it had to be a whole new woman. If I'm going to do what I do well, I have to be free to do it."

Sheesh. Talk about blowing smoke up someone's ass. To what end, I don't know. It's like Shinola getting shit's blessing before removing the smelly scuffs from your loafers. But Maggie was right about one thing: It wouldn't have done any goddamn good to try to imitate Katie, unless she thought wooden, expressionless acting that nearly ruins an otherwise flawless film was good for the role. Fortunately, unless Maggie knocks back a half bottle of Prozac and bathes in Botox, she could never be as stiff and inexpressive as Holmes was in Batman Begins.