
Justin performed "Sorry".
This year's Miss Teen USA telecast made for a fast-paced, exciting, polished two hours of television, as Miss Universe Organization (MUO) co-owners Donald J. Trump and National Broadcasting Company picked up where they left off with their fabulous Miss Universe success in May. Mario Lopez and Brooke Burns made a winsome couple as co-hosts, and the appearances of pop singers Jessica Simpson and Justin Guarini were well presented so as not to bog down the pace of the competition.
http://www.pageantrymagazine.com/magazine/features/2003/d03/d03teenusawebed.html
Miss Teen USA 2003, the 21st Miss Teen USA pageant, was televised live from Palm Springs on 12 August 2003. At the conclusion of the final competition, Miss Oregon Teen USA Tami Farrell was crowned by outgoing queen Vanessa Semrow of Wisconsin.[1]
Prior to the live telecast, the 51 contestants competed in a preliminary presentation show where they were judged in swimsuits and evening gowns. Scores from this judging determined the top 15 for the final competition.
This was the first year that the pageant was held in Palm Springs, which would later host Miss Teen USA 2004 and Miss Teen USA 2006. The pageant location was announced on 17 July 2003.[2] On 23 July 2003 it was announced that Jessica Simpson and Justin Guarini would appear as musical guests during the pageant.[3] The event was hosted by Mario Lopez and Brooke Burns.
http://en.wikipedia.org/wiki/Miss_Teen_USA_2003