On 10 September 2008, Theo Walcott scored his first hat-trick. And it just happened to make him the youngest player ever to do so for England.
Only 19 years old at the time, Walcott had risen to prominence at Southampton (2004-06) before moving to Arsenal in January 2006. After only a half season in London, England manager Sven-Göran Eriksson surprised everyone by including Walcott in his squad for the 2006 World Cup. The winger made his first start for the senior England team in a May 2006 friendly against Hungary, becoming the youngest debutant in the national team's history.
After falling out of favor with Eriksson's replacement, Steve McClaren, Walcott returned to the national team set-up under McClaren's successor, Fabio Capelli, and got his first competitive England start on 6 September 2008 in a World Cup qualifier against Andorra. He failed to score in that match, but got his chance four days later in a qualifier against Croatia.
Playing before a crowd of 35,000 at Maksimir Stadium in Zagreb, Walcott scored his first senior England goal in the 26th minute, as an attempted clearance by Croatia deflected off one of their own players. It landed at Walcott's feet on the right wing and he fired it across the keeper into the far bottom corner. The second goal was a nearly identical shot, delivered in the 59th minute.
The best goal of the three was the final one. In the 82nd minute, with England winning 1-3, forward Wayne Rooney sent a perfectly-placed pass to Walcott, who was sprinting down the right side. He outpaced his marker, took a couple of touches to move the ball across the box to the left, and slipped it under the keeper into the right corner. He was 19 years and 178 days old at the time, making him not only the youngest player to score a hat-trick for England, but the youngest to score for them in a World Cup qualifier.
Almost two years later, he got his first club hat-trick, scoring three in Arsenal's 6-0 win over Blackpool on 22 August 2010.