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