Happy Wars was accidentally released to Xbox One today, however developer Toylogic pulled the game shortly after but not before some players got hold of it.
The free to play game which has no current release date was released after a system glitch made it available. Players who did manage to download the game and have played Xbox One version will find that their Xbox 360 version is now unplayable.
Toylogic posted on their Facebook page
URGENT NOTICE REGARDING THE MISTAKEN RELEASE OF HAPPY WARS for XBOX ONE
IMPORTANT: Please note that after playing Happy Wars for Xbox One, the current version of Happy Wars for Xbox 360 will no longer be playable.
Official release of Happy Wars for Xbox One is planned in the near future, so please refrain from installing and running Happy Wars for Xbox One until that time.
The issue of Happy Wars for Xbox 360 becoming unplayable will be resolved by the next title update of Happy Wars for Xbox 360. However, if you have already installed and played Happy Wars for Xbox One, we sincerely apologize for the inconvenience this has caused you.
The free to play battler title released on Xbox 360 and has been downloaded over 6 million times, when the game releases on Xbox One (with Xbox Marketplace currently saying 24th April but this is unconfirmed) the game will have cross-platform support.