You can’t teach an old dog new tricks. Especially not an old hot dog. Filler, filler, preservative, pig lips, bun, mustard. But Dennis, Daniel, and David Lee — the Korean brothers behind Happy Belly hot dog carts — are trying to teach the mighty weiner to heel. Or heal, actually, with healthier versions of the ballpark favorite: Local Schwarz dogs come in all-beef, chicken lemon, and bratwurst options. And that’s only one of the tricks up their sleeves. They also serve sandwiches from Namu, their Inner Richmond hotspot. We’re lining up for Pan-Asian bagnat (tuna, Fuji apples, kalamata olives, toasted seaweed, sesame seeds, lemon, and scallions) and Sumi charcoal-grilled BBQ chicken with soy-glazed onions. Treats like It’s It ice cream sandwiches and mochi buns hit the sweet spot. There are three locations throughout Golden Gate Park (by the Conservatory of Flowers, the de Young, and Spreckels Lake) and one by Ocean Beach. Carts are available for private events, so consider rolling one out for your next birthday or company picnic. We triple dog dare you. Hours of operation, 11 a.m.-6 p.m. For menus, go to happybellyfoods.com or e-mail firstname.lastname@example.org.