Back in the day, it was a free-for-all inside your Scooby-Doo lunch box. Your PB&J sandwich got panini pressed by your thermos, which slowly dripped fruit punch on a note from Mom.Fast-forward to PlanetBox, a locally designed and sustainably made stainless steel lunch system that’s about to change the midday meal forever. Combining the serendipity of a bento box with the sturdiness of a military-rations tray, it safely transports as many as seven dry and wet foods at a time.Little diners can change its look with a decorative magnet set that comes in thirteen kid-friendly designs (rainbows, rockets, and trains). When the day is done, pop the box in the dishwasher to clean.Best part: There’s a pocket for special paper messages. After all, the more things change, the more they stay the same.Available online at planetbox.com, $35-$60.Photo: Courtesy of PlanetBoxGear up before the back-to-school rush with our picks for the best backpacks and lunch boxes. STROLL38th Annual Nihonmachi Street Fair What: A free foodie-pleasing fest with games and crafts dedicated to the people of Northern Japan.Why: Meshiagare!When: Sat. & Sun., 11 a.m.-6 p.m.Where: Post St., b/t Laguna & Fillmore Sts.CREATEPuppet-Making Party What: Puppeteer Meghann Jordan teaches tots to construct their own hand moppets.Why: Acting out is healthy.When: Sat., 2-4 p.m.Where: Paxton Gate’s Curiosities for Kids, 766 Valencia St., b/t 18th & 19th Sts. (415-252-9990). Free.ROASTNatureBridge Family Hike and Campfire What: Take a walk with the kids under the glow of a full moon.Why: Day is done, gone the sun.When: Sat., 6-8:30 p.m. Where: Headlands Institute, Rodeo Beach, 1033 Fort Cronkhite, near Bunker Rd., Sausalito. Registration (required) online at aug13nighthike.eventbrite.com. Adults and children, $10.