It is encouring its fans to come up with ways of showing their love for Greggs, whether it be changing their name on Facebook, creating a song, or dressing up as a life size sandwich.
Graeme Nash, head of customer and marketing at Greggs said "Some of our customers have a great sense of humour and many are extremely passionate and creative. We are really excited to see how far they will go."
The campaign, created by Steel, runs for the next two weeks, with the winners being selected based on their creativity and flair.
Greggs, which has more than 1,600 shops nationwide and claims to serves over six million customers a week in the UK, has grown its Facebook page from 50,000 fans to half a million over the past two years.
The campaign taps into the trend for brands to identify and reward their biggest advocates in social media.
Unilever’s Marmite recently ran a competition to enlist more superfans into its ‘Marmarati’ secret society.