Where You've Seen The Letterkenny Cast Before Letterkenny is a charming town with a deep-rooted sense of community. Everything about Letterkenny is special, especially its inhabitants. One particular resident who has stolen the hearts of many is the delightful Katy. Catherine brings affection and joy to Letterkenny, County Donegal with her charming presence. She is adored by everyone who crosses her path. Letterkenny, Ireland Katy is a match made in heaven!