At 18 years and 299 days old, Littler becomes the youngest PDC world No. 1 on record, surpassing Michael van Gerwen's previous mark of 24 years and 251 days set in 2014.
The numbers alone illustrate the scale of the achievement, although the manner of his rise has been even more striking.
Since lifting his first world title at Alexandra Palace in January, Littler has added the World Matchplay, World Grand Prix and UK Open to a catalogue of trophies that already includes wins at the Australian Darts Masters, New Zealand Darts Masters, Belgian Darts Open, Flanders Darts Trophy and Players Championship 32.
His dispatching of Noppert showed the same combination of composure and precision that has defined his second season on the circuit.
Before the Grand Slam, Humphries held a £72,000 cushion over him in the rankings, yet Littler's return to the final has swung that gap to £81,500 in his favour.
A win on Sunday would stretch the margin to £161,500 and crystallise the power shift that has been brewing for months.
Littler, typically unflustered, told Sky Sports: "It's not even been two years on the tour and I'm already world number one.
"That's job done. But now I've got a bigger match later tonight. I've said it throughout the year that Luke Humphries was the best in the world. Now I am the best in the world. It's another Luke versus Luke final, some like it, others don't.
"It's going to be another brilliant game. I've still not been beaten here. Hopefully I can go back-to-back tonight."
Humphries sinks Price
Humphries, who prised the No. 1 ranking from Michael Smith in 2023 and has since stockpiled the World Championship, Premier League, World Matchplay, Masters, World Cup and multiple Players Championships, reached the Grand Slam final after a 16-13 win over Gerwyn Price.
His reaction to Littler's rise offered both honesty and defiance.
"This could be my last day as world No. 1, who knows? But it's not about that tonight, it's about picking up this trophy, which really started my career off," he said.
"I know it sounds crazy, but I hope he wins. He's probably going to take it off me anyway.
"If Danny wins, that's great for more, but a great final against Luke is a prospect I always enjoy. When I get to the Worlds I'll be fighting hard to take it back off him. It's war now. I'm going to try and take it back."
The PDC ranking system, which tallies prize money over a two-year rolling period, has played its part in the current standings.
Humphries has spent the season defending the significant sums he earned during a dominant 2023, while Littler has been adding fresh winnings at a relentless rate.