Betway World Cup of Darts top seeds Scotland suffered a surprise 5-2 defeat to Singapore in the first round.
Gary Anderson and Peter Wright were shocked by Paul Lim and Harith Lim in a huge upset.
"When we drew Scotland we knew it would be tough, regardless," Lim said afterwards.
"But I always say in any tournament, if you beat the number one seed, you become the number one seed. I always felt the pressure was on them."
The surprise result was secured by a nerveless 100 checkout from Lim, who struck a nine-darter at the World Darts Championship 27 years ago.
Singapore struck the first two 180s before Anderson and Wright, the world number two and three respectively, had got into their groove.
Lim hit double 20 for a 3-1 lead before missing the same shot twice in the next leg, allowing Anderson to reduce the deficit.
But Lim took advantage of Wright's profligacy to hit double eight to move within a leg of victory.
When Anderson then landed in the wrong bed altogether, Lim took his chance to check out from 100.
"I told myself: give me the shot, and I've got to make use of it," Lim said. "When he gave me a chance I had to take it, and I was lucky."
Singapore will now face Spain, who were provided with a serious test before the pairing of Antonio Alcinas and Cristo Reyes prevailed in a 5-3 victory over Japan.
The Japanese side of Haruki Muramatsu and Yuki Yamada raced in to a 3-1 lead before a run of four straight legs confirmed the victory for the Spanish.
The 2017 Betway World Cup of Darts opened with the Greek team of John Michael and Ioannis Selachoglou having to battle back from 3-1 down to overcome Thailand in a 5-3 victory.
The Greeks will face Belgium who needed an impressive individual performance from Kim Huybrechts to help pull himself and his brother Ronny past New Zealand.
The match looked a tough draw for 2013 finalists Belgium but world number 12 Huybrechts showed his class hitting four maximums, as they ran out 5-2 winners.
“Ronny and I know that even when one of us played badly, the other can pull us through," said Kim.
“I played well today but I know next time I might need Ronny and I believe he will be there for me.”
Eighth seeds Australia then had to survive a match-dart as they snuck past Denmark to reach the second round.
The team of Kyle Anderson and Simon Whitlock were expected to have far too much for Per Laursen and Alex Jensen but the Dane’s had other ideas.
The third leg saw Australia break throw but Laursen returned the favour in the very next leg, taking out 116 to break back and level the match.
The encounter then went with throw until the deciding leg where Laursen missed tops for an unlikely win.
Whitlock, who was struggling with a wrist injury needed his partner to land the winning double.
“I needed my partner there,” said Whitlock.
“My wrist is in a lot of pain so I just had to stick in there and let Kyle do the business.” Added the ‘Wizard’.
Kyle Anderson, who is making his second appearance at the Betway World Cup of Darts was happy to take the lead role.
“I had to play well tonight and I think I did that.
“I started a bit nervy but once I found my range it was all ok. Im delighted to get through that one," said Anderson.
Australia’s second round opponents will be Russia as Borris Koltsov produced a moment of magic to secure their place in the next round as they beat Hong King 5-3.
With the match going with throw the Russian took out 111 on double 16 to break the throw, a break which would ultimately win them the match.
The Republic of Ireland booked a second round clash with Wales after beating Poland 5-3 in a close encounter.
William O’Connor started the match in style, taking out 106 to hold in the opening leg of the match.
However, it was Poland who were first to break the throw, pinning tops in the fifth leg for a 3-2 lead.
Mick McGowan then found double eight in the very next leg to break back immediately as Ireland went on to win three legs in a row and seal the win.
Mark Webster and Gerwyn Price had to average 100.14 and survive two match-darts as Wales snuck past Finland in a last leg decider.
The final match of the opening day of action in Frankfurt began with Finland moving in to a 2-0 lead to put the pressure on Wales.
However, Webster rose to the occasion taking out 124 on the bull to break back immediately.
The match then went with throw, including a seventh leg 141 finish from Finland as the match went to a deciding leg.
Finland then had two opportunities to win the tie but Kim Viljanen missed two darts at tops to seal the victory.
It was Webster who found the winning double, pinning double five before speaking of his relief.
“That was tough! The guys played so well but fortunately I had Gerwyn with me, he was brilliant.
The scoring from him was great and fortunately I was there to tidy it up at the end.”
Price who hit four maximums and a 177 during the game was pleased with the win.
“It’s great to get over the line, I scored well but this is a team game and Mark hit the most important double of the night,” said the 32-year old.
The first round concludes on Friday evening with the remaining eight games, including reigning champions England - represented by World Cup debutant Dave Chisnall and Adrian Lewis - up against Gibraltar's Dyson Parody and Dylan Duo.
Thursday's results
First Round
Thailand 3-5 Greece
Hong Kong 3-5 Russia
Republic of Ireland 5-3 Poland
Japan 3-5 Spain
Belgium 5-2 New Zealand
Australia 5-4 Denmark
Scotland 2-5 Singapore
Wales 5-4 Finland