Giant cardboard boxes, fabric scraps, bottle caps, and wood bits—Marie Kondo would most likely consider such a collection of stuff to be junk, but to the Children’s Museum of Sonoma County, it’s fodder for invention. Kids can use these and other materials to design and build imaginative creations at the Museum-on-the-Go’s free Pop-Up PLAY event at Rohnert Park–Cotati Regional Library in Rohnert Park on March 18, 11 a.m.–12:30 p.m.