The NRL estimates around $1 million has been raised for Arrow since May, when a diagnosis of motor neurone disease forced the South Sydney forward into retirement.
His 31st birthday coinciding with Sunday's clash between Souths and Newcastle, Arrow was thrown the "world's biggest birthday party" by the NRL.
Arrow himself was on hand, the same week as he married long-term partner Berina and attended Wednesday night's State of Origin decider.
"Unreal. I'm truly honoured to be here," Arrow told Fox Sports before the Rabbitohs' 26-24 win.
"I want to thank everyone from the bottom of me and my family's heart. I get emotional thinking about it (the support)."
Hundreds of fans queued up in party hats waiting for Accor Stadium's gates to open at 12.30pm, while others secured theirs on entry.
The NRL printed some 10,000 hats to distribute on game day, and thousands more were sold online by fans showing their virtual support.
Sunday's game-day raffle was pledged to Arrow and his family, with the visiting Knights making a donation as well.
The Wiggles performed live entertainment at halftime, when officials rolled out a giant 120kg birthday cake in the shape of Arrow's old Souths jersey.
Prime Minister and lifelong Rabbitohs fan Anthony Albanese was on hand as the cake was cut and 'Happy Birthday' was sung.
But the most jubilant scenes were saved for after the Rabbitohs' surprise two-point win, with the crowd of 30,113 permitted onto the field to celebrate.
Souths chief executive Blake Solly and Australian Rugby League Commission chair Peter V'landys presented Arrow with his birthday present - a commemorative framed jersey featuring his three NRL clubs as well as Queensland.
"I love you all, thank you," Arrow said to the crowd after the presentation.
The NRL will submit footage to the Guinness Book of World Records for assessment, but are confident of having broken the standing mark of 1,924 people wearing party hats.
That figure was achieved at Ohio State University last year as students held birthday celebrations for the school's mascot.
Arrow and wife Berina will fly to the US next week to attend the FIFA World Cup final.
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