The veteran made a bright start with a 120 checkout to secure the first set, but 18-year-old Hopp responded with a 12-darter to help him level the scores.
Hopp had a chance to go in front in the third set, but he missed four darts for the win and King took full advantage. However, King then missed a chance of his own to secure the match, allowing Hopp to force a decider.
The youngster grabbed the opportunity for an upset in style, hitting a 161 checkout to knock King out at the first hurdle.
Lewis, who took the title in 2011 and 2012, clocked a 101.9 three-dart average to dispose of Pallett and set up a second-round match with Keegan Brown.
Bunting barely broke sweat as he cruised into a two-set lead on his bow on the big stage, but Marijanovic - who beat Jermaine Wattimena in the preliminary - rallied and reduced the deficit after the break.
Normal service was resumed in the fourth set, however, as Bunting raced into a two-leg lead before sealing his place in the next round with an impressive 124 checkout.