Littler returned to Alexandra Palace to a rapturous welcome from over 3,000 fans and produced a stunning fourth set display.
He was on the maximum after his opening two throws in the first two legs and finished the set in 32 darts – the minimum possible is 27.
The youngster will next play European Championship winner Richie Edhouse, seeded 29, or Ian White after Christmas, and has been seeded to meet Humphreys in the semi-finals.
After entering last year’s event ranked 164th, Tanger is ranked fourth in the world and would move to second if he reaches the final again this time.
He won 10 titles in his first professional year, including the Premier League and the Grand Slam of Darts.
After reaching the final of the World Championship as a debutant aged just 16, Littler’s life changed and his interest in darts grew.
Google says he was the most searched athlete online in the UK during 2024.
This Christmas, more than 100,000 children are expected to open Little brand magnetic dartboards as gifts.
Its impact has helped double the number of junior academies and fueled plans to expand the World Championship.
Littler was named the BBC’s Young Sports Personality of the Year on Tuesday and was runner-up to athlete Kelly Hodgkinson for the main award.