The pub in Irish dramas is a center not just of drinking, but also of telling tall tales. In J.M. Synge’s Playboy of the Western World, a new arrival, Christy Mahon, boasts of killing his father. In Conor McPherson’s The Weir, the regulars exchange ghost stories. But the atmosphere of Catch of the Day, by Megan Jenkins and the Red Fox Theatre company, is different. There’s music already happening on stage when one enters, and the gregarious cast may be engaging the audience in conversation or offering potato chips up and down the aisle or sniping at one another. The slapdash mix of music and comedy is more goulash than ghoulish, yet the lack of structure turns out to be one of the show’s charms.