Clicking through the Arcade recommendations for the Halloween themed promotional page reveals Zombie Wranglers is intended to be released in October but clicking on the title actually reveals it is already available for purchase on the service for 800MS points. Unfortunately no demo is available, which is why we assume the title was accidentally placed on the service.
Looking forward to Zombie action? Get it while it's hot ... because as soon as Microsoft discovers it, it will most likely be pulled for the actual planned release date. More images of the menu after the jump.
Ed. Note: When searching through the Xbox Live Arcade titles normally, Zombie Wranglers is not listed and can only be found if you come across a promotional banner for Shocktober - which pops up randomly among other ads. We've only had the ad appear on accounts in the USA.
[Update: The content is listed but not available for download at this time.]
[Thanks, FR3SH JIV3]