An unknown number of Xbox Live subscribers have received an email from Microsoft that offers them a full copy of Xbox One digital launch title Killer Instinct on 22nd November.
The email states that the recipient will get a version of the game with all characters unlocked from the off. Further instructions will follow on the 22nd, the day of Xbox One's launch.
"You're a fan of ours and we're a fan of yours," the email begins. "Thank you for your dedication to Xbox. We want to show you our appreciation, so we're giving you Killer Instinct."
"We've selected a bunch of our Xbox fans for their support and as a celebration for the upcoming Xbox One," Xbox Support explained. But the help service refused to offer more details on how the winners were chosen - or whether more emails might be sent.
Gamers with and without the email have been comparing Xbox Live stats to try and determine Microsoft's methods for picking Killer Instinct winners - with little success.
Some recipients have the Xbox One Pre-order Achievement - but others don't. Some have been beta testers - others have not. Some have nearly a decade of Xbox Live under their belt - others don't.
"We don't have any specifics on that other than that some users have received a gift," a representative wrote. "We considered a variety of things like Gamerscore, Live tenure and other factors in markets where Xbox One is available."