Nabisco is having a little fun with fans of one of its most popular cookies. The Mystery Oreo contest is about to get underway, with a $50,000 grand prize for guessing the flavor of the crème inside the limited-edition cookies made especially for the event.

People can begin submitting entries online or by email on Sunday for a chance to win the sweepstakes.

According to the official rules, no purchase is necessary, and there are several ways to submit multiple entries.

More information about the contest may be found at MysteryOREO.com.