Colleen’s of Medford Square is hosting a holiday pop-up featuring Mystic River Clay, a Medford-based company created by Emma Heffern and Mandy Byrnes that specializes in clay ornaments. They will be joined by three generations of crafters, with holiday decor items offered from Inspired by Nature, shrubs by Linda D’Ambra, and soy candles from The Prickly Pear. Venmo and cash accepted. Plus, the Girl Scouts will be on hand selling cookies.