The big names delivered again as the Group B teams made their second appearance, in the fourth meeting of the inaugural International Swimming League programme, over two nights at Duna Aréna, Budapest.
About $180,000 (£140,000/€162,000) in prize money is awarded at each regular season match, raced over a short course, with nearly $1.5 million (£1.2million/€1.3million) available for December's grand final in Las Vegas.
London Roar won in Lewisville, Texas, last weekend and got off to the perfect start in Hungary, as Australian Emma McKeon won the women's 100 metres butterfly, finishing well clear in 55.39 seconds.
Kendyl Stewart came second, with Roar team mate Marie Wattel third.
The big draw of the evening was next up, as Olympic 100m breaststroke champion Adam Peaty kept Roar's momentum going.
Peaty came through in the final 20 metres of the 50m breastroke to just edge out Vladimir Morozov of Iron and LA Current's Felipe Lima.
Katinka Hosszú, who is owner and captain of the Iron team, shone in front of her home crowd.
She won three events last week in Lewisville and never looked in danger in the 400m individual medley, coming home in 4 min 27.27sec, ahead of Bailey Andison and Mireia Belmonte.
LA Current were next to enter the winner's circle, as Andrew Seliskar just got home in the 400m medley in 4:03.28, ahead of Iron team mates David Verraszto and Gunnar Bentz.
London Roar came right back into things, with their second team leading home their first team in the 4x100m freestyle relay - NY Breakers were third.
LA Current won the men's 200m backstroke, thanks to Ryan Murphy cruising home ahead of Christian Diener and Markus Thormeyer.
Roar's Minna Atherton was one of the star performers last week, and she followed that up with another victory in the 200m backstroke in a time of 1:59.48, just 0.2 outside the world record, ahead of Hosszú.
Later in the evening, Atherton delivered again, winning the 50m backstroke in 25.8.
In other big results, Kyle Chalmers led Roar to their second relay win of the night in the 4x100m medley.
Morozov got revenge in the 50m freestyle in a time of 20.68, ahead of Kyle Chalmers and Nathan Adrian.
The brilliant Russian then helped Iron to victory in the 4x100 freestyle relay.
With day two still to come tomorrow, London Roar top the table with 251.5, while LA Current lie second on 212.5.
Iron sit in third on 203.5 as the NY Breakers bring up the rear on 142.5.