Here's a head-scratcher. A game listing for something called Zelda Universe has appeared on the Entertainment Software Rating Board's site.
The mystery game, which has been handed an E for Everyone rating, lists its publisher as Nintendo and its platform as 'online'.
Given its title and that small collection of facts, an online Zelda MMO is the obvious guess, but that seems highly unlikely given Nintendo's attitude to both online play and developing games for platforms other than its own.
Zelda Universe is the name of the franchise's official website, but then the ESRB doesn't rate web content. Some kind of game embedded in the site then? Again, that doesn't really some like something Nintendo would do.
Perhaps it relates to the series' 25th anniversary, which comes around later this year. During his GDC keynote in March, Nintendo CEO Satoru Iwata announced it was planning something special to mark the event.
It could of course just be a mistake, but it's worth noting that this isn't the same as a trademark listing a product has to physically exist for the ESRB to give it a rating.
Maybe we'll learn more at E3 next month.