BROCKTON — Before Sunday, few Brockton residents had ever seen a little town in Ireland called Mullingar.

But as more than 1,500 revelers gathered in downtown Brockton wearing red-and-white Santa hats, they were met with a giant television screen with a grainy video feed straight from the Irish town 50 miles west of Dublin: Thousands of Mullingar residents waved back at them, all clad in Santa hats.