All of the fairies that were present in the Enchanted Forest became nun's in Storybrooke. Nuns play an important role in Christianity. The nuns in Storybrooke are part of a Convent - The Sister's of Saint Meissa. Within their group they help organize special events for the town, help fundraise and do community service. 

 

The town of Storybrooke, had a festival for Miner's Day. During this time they decorated the town and sold candles as a fundraiser to keep the convent open, as their landlord was Mr. Gold (the Devil). The nuns are most often shown wearing crosses around their necks and having a white collar. 

When the dark curse is broken, someone asks David Nolan: "Are the nuns still nuns, or can they, you know, date?". This is referencing a well-known oath that Roman Catholic nun's must take when entering the sisterhood.