Newtown will celebrate its 63rd Labor Day Parade on Monday, stepping off at 10 a.m. with this year’s theme, “Pets on Parade.” Floats, marching bands, vintage cars, and community groups will line Main Street, with retired animal control officer Carolee Mason serving as grand marshal. Roads along the parade route will close at 9:30 a.m., including portions of Route 25, Queen Street, and Church Hill Road.