According to a story in the Washington Post, self-described introvert Clarence Thomas, who famously has not asked a question in oral argument in seven years, sometimes asks his "friend and seatmate" to ask a question for him. In a recent Harvard Law School appearance, Justice Thomas told the students:
I’ll say, "What about this, Steve,’"and he’ll pop up and ask a question. I’ll say, "It was just something I was throwing out." So you can blame some of those [Breyer questions] on me.
Thomas is most frequently said to be aligned with Justice Scalia, who is also his seatmate, but who, judging from his prolixity on the bench, might not be so inclined to use up any of his own questioning time for others' questions.