Pen Trading and Peekaboo at President Trump's 1st Law Signing He signed Cabinet nominations in the President's Room.

 -- Sitting in the President's Room at the U.S. Capitol, with his grandchildren by his side, President Donald Trump had some fun signing the formal nominations for his Cabinet picks.

Minority Leader Nancy Pelosi smiled and told the room she got "Tom Price," meaning she received the pen used to sign his nomination. The mention prompted a response from the 45th president and praise for his pick to run the Department of Health and Human Services, Rep. Tom Price (R-GA).

"You know he's going to be terrific, and he's going to be approved, but I'll give you a different one," Trump told Pelosi. "You want Elaine?"

"Mr. President, the leader wants Elaine," Pelosi told Trump referring to Donald Trump's pick for Transportation Secretary and Senate Majority Leader Mitch McConnell's wife.

"You know what, the leader should have Elaine," Trump agreed, giving the pen to McConnell.

According to Time, it's customary for the president to use multiple pens to sign important legislation. It's a tradition that dates back to at least President Franklin Delanor Roosevelt.

Trump's 10-year-old son Barron also had some fun, playing peekaboo with Ivanka Trump and Jared Kushner's son Theodore.