May the Fourth Be with You: Star Wars Party. Flossmoor Public Library, 1000 Sterling Ave., will host Star Wars themed games, challenges and prizes. Dressing in costume is optional but encouraged. Register here.
Melody Mart Open House. Tour the music store at 18062 Dixie Highway from 10:30 a.m. to 3:30 p.m. Check out lesson studios, shop, meet instructors, try out instruments. There will be snacks. RSVP here.
Chicago Knockouts Roller Derby. Wreck League bout between Rebellion and Empire. Doors open at 5:15 p.m. Action starts at 6 p.m. at Homewood Auditorium, 2010 Chestnut Road. Tickets $15 online, $20 at the door, trackside $20, front row $25. Accessible seating available at no extra charge. Tickets available here.