Google Maps Pokemon 2
Google's first April Fool's Day joke appeared on the mobile Google Maps app. Google Maps

Google Inc. (NASDAQ:GOOG) on Wednesday started notifying users who completed its Google Maps Pokemon Challenge that a prize was on the way, but some players may be left empty-handed.

The challenge was one of the promos Google traditionally does for April Fool's Day, but not all users who found the 151 Pokemon are being notified that Google will ship a reward. AndroidPolice reports that only those who responded to a post shared by Google Maps on Twitter and Google Plus are being asked to fill out a form so that Google can send them a "small (free) token" of its appreciation.

Google did not respond to an email seeking comment.

The company released a video when it announced the Google Maps Pokemon Challenge, which showed a company-branded business card with the title of Pokemon Master -- perhaps that's the prize? Players were challenged to find 150 Pokemon characters scattered throughout the world on Google Maps, along with a secret character, Mew, that only appeared after the rest of the challenge was completed.

The company traditionally runs several pranks and promotions for April Fool's Day, and this year's promo sparked speculation that Google's partnering with Nintendo meant that the video game company was ready to start releasing games for mobile.