O'Shea started in entertainment at an early age, playing traditional Irish music and touring Europe with several groups. At college he studied theatre and starred in several theatrical productions. He worked in the National Theatre of Ireland, the Abbey Theatre. He won the Harp Newcomer Comedy Award in 2000 and performed in the BBC Newcomer Awards the same year. He was chosen to perform in the MontrealJust for Laughs comedy festival in 2005 and also The Kilkenny Cat Laughs festival in 2005 and 2006. He wrote TJ and TJ sketches on Today FM.