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Four-year-old Jack Roberts (search) was the smallest person in the East Room, but he had an outsize presence as father John took the oath to become the 17th chief justice of the United States.

Jack sat, politely if a bit fidgety, in the front row with his family. It was nothing like his performance during President Bush's July announcement of the elder Roberts as his pick for the Supreme Court. Back then, Jack danced enthusiastically — and distractingly — in front of the lectern throughout the president's remarks.

Despite his toned-down appearance on Thursday, Jack warranted a mention in the remarks delivered by both the president and his father.

"It's a proud day for John Roberts' (search) family. We extend a special welcome to his wife Jane, their daughter Josie and son Jack," Bush said, pausing as the audience erupted in laughter. Then the punch line about young Master Roberts: "a fellow who's comfortable with the cameras."

After taking the oath, John Roberts offered thanks to all the people who contributed to his confirmation. The Senate Judiciary Committee (search) in particular, he said, "faced a very special challenge."

"And yet, working together, we met that challenge. We found a way to get Jack into the committee room, introduced to the committee and back out again without any serious crisis," Roberts said. The mention of his son drew more laughs.

Jack's mischief has apparently been on public display before. Two years ago, during Senate confirmation hearings on Roberts' nomination to a seat on the federal court of appeals in Washington, D.C., Jack and his now-5-year-old sister Josie were present and, it seems, making some noise.

"The committee has already heard some unscheduled testimony from my children, Josephine and Jack," Roberts joked then.

Also at Roberts' White House swearing-in were other members of his family, including his parents, Rosemary and Jack Roberts, and two of his three sisters.