From a Slate article touching on Colin Powell's testimony this week to the House Internatiional Affairs Committee:
There [Colin Powell] sat, recounting for the umpety-umpth time why, back in February 2003, he believed the pessimistic estimates about Iraqi weapons of mass destruction. "I went and lived at the CIA for about four days," he began, "to make sure that nothing was—" Suddenly, he stopped and glared at a Democratic committee staffer who was smirking and shaking his head. "Are you shaking your head for something, young man back there?" Powell grumbled. "Are you part of the proceedings?"
Rep. Sherrod Brown, an Ohio Democrat, objected, "Mr. Chairman, I've never heard a witness reprimand a staff person in the middle of a question."
Powell muttered back, "I seldom come to a meeting where I am talking to a congressman and I have people aligned behind you, giving editorial comment by head shakes."