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