With only seven NRL games to his name, the 18-year-old winger became the third-youngest debutant in Kiwis history when he replaced the injured William Warbrick at CommBank Stadium.
McLean had already appeared a strong chance of replacing Sunia Turuva on the wing at NRL powerhouses Penrith next year, but after Sunday's masterclass it will surely be impossible for Ivan Cleary to resist starting him in Las Vegas in round one.
The young gun combined effortlessly with halves Charnze Nicoll-Klokstad and Shaun Johnson, the latter playing his last game after coming out of retirement to assist the injury-hit Kiwis.
Charnze Nicoll-Klokstad scored a try in New Zealand's crushing win over PNG. (Dean Lewins/AAP PHOTOS)
McLean had the first try of the game on the back of a long cut-out pass from Nicoll-Klokstad, before deftly scooping up a Johnson kick on the left edge to help extend the lead to 28-6 after the half.
A Nicoll-Klokstad kick sent him over a third time, before McLean entered rarefied air from a Johnson long ball midway through the second stanza.
Only once in history has a Kiwis player scored more tries in a game than McLean - lock forward Hugh McGahan crossed six times against Papua New Guinea in Auckland in 1983.
Keano Kini was equally impressive to cap off his debut series with the Kiwis, running for 301 metres and outshining in-form rival fullback Nene MacDonald.
Johnson, meanwhile, signed off in style with a beautiful pass to Naufahu Whyte that helped the Kiwis reach 50 points.
Winger Jamayne Isaako notched a hat-trick of his own with a runaway try in the final minutes as the Kiwis went into party mode.
The win means the previously out-of-form Kiwis have avoided relegation from the Pacific Cup to the second-tier Pacific Bowl competition at the 2025 Pacific Championships.
Despite the one-sided result on Sunday, the series will give the Kumuls reason for optimism on the road to both the 2026 World Cup, and the Pacific nation's push for NRL inclusion.
PNG won both their previous two matches and were the better team for much of the first half against New Zealand, but struggled for execution bombing three tries.
Hooker Liam Horne could have given the Kumuls the lead had he grounded Lachlan Lam's grubber kick, before Rodrick Tai was called offside in the lead-up to Rhyse Martin's would-be try.
Winger Robert Derby bungled yet another chance for points by fumbling the ball close to the line.
The Kiwis made PNG pay for their missed chances by scoring back-to-back tries in the final two minutes before the break.
First it was off-contract Leo Thompson charging over to drop the latest reminder of his potential value on the open market, before McLean tore down the left edge after the siren.
He passed inside to Nicoll-Klokstad, who made it 22-6 at the break and gave the Kumuls a big mountain to climb.
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