Apparently, Mary-Kate and Ashley Olson are a tough pair to work with.

This is according to shoe mogul, Steve Madden who worked with the mega-rich twins for five years on their two shoe lines.

Madden said during an interview, “They’re very demanding, they’re very tough. You know, just tough, tough. They want what they want. And so we worked hard to get that done.”

Madden is 54-years-old, more than twice their age, and yet they still have him shaking in his custom designed boots.

“They are difficult. They are exacting,” added the famous shoe designer. “They are a pain in the ass. But they’re very good though.”

But even though the twins strike fear in the eyes of anyone who works with them, Madden says their business relationship works.

“They’re very grown up, very worldly. And I’m very immature. So we meet in the middle.”

Those girls must be constantly hungry… you don’t mess with hungry women.