Littler averaged 105.05, the tournament's highest so far, and hit six 180s to beat the Irish number one and set up a second-round meeting with Nathan Aspinall.
“I’m happy with the win,” said Littler, who secured only his second victory at the Westfalenhalle.
“I meet Nathan again tomorrow. I’ve just got to take it game by game.
“Obviously, it’s the last one missing, so I can’t put too much pressure on myself. I’m just happy to get back on stage and do my job.”
Aspinall booked his place in the second round by coming from behind to beat Cristo Reyes, reeling off four consecutive legs with finishes of 134, 112 and 90.
Doets produced one of the night's biggest upsets, beating fellow Dutchman Van Gerwen 6-3 on his European Championship debut. He took out 106 before hitting a 132 checkout on the bullseye to establish a 3-0 lead and sealed victory with a 12-dart leg.
“It was a tough game,” Doets said.
“The draw comes out and I get Michael (…) it’s still Michael van Gerwen. He is the one I looked up to for years and the most successful player from the Netherlands.
“He didn’t play like he can, but I’m really happy to win. I felt through the whole game that I was the better player.”
Doets will face Krzysztof Ratajski on Saturday. The Pole extended his winning run against Dave Chisnall to eight matches, securing only his second European Championship victory in eight appearances.
Martin Schindler delighted the home crowd by beating second seed Wessel Nijman in a deciding leg. The German number one, who secured his place in the 32-player field at the final European Tour event of the year, converted 55% of his attempts at doubles as he capitalised on Nijman’s wastefulness.
“I’m very happy at the moment,” Schindler said. “I was really nervous, especially in the last leg.
“Right now I feel over the moon and very confident. Tomorrow is a new day and I will need to focus again.”
Jermaine Wattimena will face Schindler after beating Ryan Joyce 6-3, despite missing two darts to complete a whitewash.
Jonny Clayton and Josh Rock also advanced with convincing victories. Clayton beat Niko Springer 6-3, while Rock won six consecutive legs to defeat Chris Dobey 6-1. They will face each other in the second round.
The European Championship continues with two sessions on Saturday, when the remaining 16 players return for the second round. Defending champion Gian van Veen faces Luke Woodhouse in the afternoon, while Littler and Aspinall meet in the evening.
Results
Jermaine Wattimena 6-3 Ryan Joyce
Krzysztof Ratajski 6-2 Dave Chisnall
Nathan Aspinall 6-3 Cristo Reyes
Jonny Clayton 6-3 Niko Springer
Luke Littler 6-3 William O'Connor
Martin Schindler 6-5 Wessel Nijman
Kevin Doets 6-3 Michael van Gerwen
Josh Rock 6-1 Chris Dobey