The defending champion averaged 113.68 and opened the contest with the perfect leg before missing a second nine-darter four legs later after wiring double 15.
Despite averaging 12 points fewer than Littler, Aspinall fought back to level at 7-7.
Littler responded by winning the next three legs before missing a match dart at 10-7, allowing Aspinall to extend the contest with a 170 checkout.
The world number one made no mistake in the following leg to book his place in the quarter-finals.
"It felt amazing. That was probably the best game me and Nathan have played against each other," Littler said.
"I've seen the averages there, 113 for me, 101 for Nathan. I thought Nathan's average was going to be a bit better!
"As soon as I missed double five, I knew he was going to hit the 170. I'm just glad to take part in such an amazing game."
Littler hit 14 maximums and had just six visits without a treble during the 19-leg contest, while the pair's combined 22 180s set a new record for a World Matchplay second-round match.
He will face Josh Rock on Thursday after the Antrim native beat Liverpool's Stephen Bunting 11-6.
Rock pulled clear after a slow start, taking out 106 to lead 6-3 before wrapping up victory with a 140 finish to reach the quarter-finals for consecutive years.
"That was probably one of the toughest games of my life," Rock said.
"Stephen is one of my best friends on the tour, and I had to change my mindset. I'm going to give it my all against Luke, because I'm here to win this title."
Elsewhere, Dirk van Duijvenbode edged past compatriot Michael van Gerwen 14-12 in a deciding tie-break to reach the quarters for only the second time.
The towering Dutchman led 8-4 before three-time champion Van Gerwen fought back, cutting the deficit to a single leg with an 11-darter and a 148 checkout.
Van Duijvenbode regained control by breaking throw with an 11-dart leg at 12-12 before sealing victory.
He will play Gary Anderson after the Scot beat Jonny Clayton 11-7 to reach his first World Matchplay quarter-final since 2020.
Clayton led 4-1 after a 121 checkout, but Anderson won eight of the next 10 legs before sealing victory with a 12-darter.
"I'm a big fan of Jonny. He's a gentleman and a cracking, cracking darts player," Anderson said.
"I'll keep going, but it just proves the point that the old boys aren't finished yet."
The second round concludes on Wednesday with Gian van Veen facing fellow Dutchman Wessel Nijman, Cameron Menzies taking on Ross Smith, Gerwyn Price meeting Rob Cross and James Wade playing Ryan Searle.
Tuesday's results
Gary Anderson 11-7 Jonny Clayton
Dirk van Duijvenbode 14-12 Michael van Gerwen
Luke Littler 11-8 Nathan Aspinall
Josh Rock 11-6 Stephen Bunting