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