They grow up so fast. (Kevork Djansezian/Getty Images)

Such was the case two Decembers ago when the POTUS thanked a still-only-15-years-old Justin Bieber at “Christmas in Washington,” the annual holiday concert telecast that returns to the National Building Museum this Sunday. (TNT will air it on Dec. 16). The almighty Bieber is also set to return to the Building Museum this year — a triumphant “Christmas in Washington” homecoming after 24 months at the highest heights of pop popularity.

Read the profile we reported at that 2009 concert — back when Bieber didn’t really know all the words to “Hark! The Herald Angels Sing” — right here.