Every morning, much of Penang sits down to a bowl of koay teow th’ng: wide rice noodles in any combination of duck, pork or chicken broth with floating fish balls and hunks of meat, all garnished with crispy browned garlic.

The dish, thought to be an iteration of a noodle soup introduced to the island by Chaozhou immigrants, may well be the island’s most popular. So ubiquitous is it between 7 a.m. and noon that at least seven koay teow th’ng stalls operate simultaneously within a three-block radius of my George Town home.

Yet I rarely see tourists among the throngs of eaters. Most visitors to Penang, even those well versed in local street foods – Malaysians and Singaporeans excepted – seem unaware that the dish exists.

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It isn’t the only Asian street food to be loved by locals but ignored by visitors. Tourists pound Bangkok’s pavements in search of the perfect pad thai but pass on koay teow lad naa, flat rice noodles stir-fried with black soy and doused with mild gravy. Travellers to Hanoi seek out pho, yet overlook northern Vietnam’s bun ca, rice noodles in a dill-fragrant tomato and seafood broth with fish. Perhaps the best example of a hometown favorite unloved by (mostly Western) foreigners is congee in Hong Kong.

“I’m not flying all the way to Asia to eat rice porridge,” an acquaintance responded recently when I advised her to seek it out during her three-day stay in the SAR.

I’ve often wondered what makes some local specialties sing in the eyes of visitors while others go neglected. Some suffer from the Plain Jane Syndrome: a combination of monochromatic appearance and deceptively simple preparation that reduces surface appeal. To the uninitiated, congee appears to be little more than a creamy near-paste of overcooked rice; it’s only natural that many would pass it over in favor of golden egg noodles garnished with succulent pork.

And then there is what Leela Punyaratabandhu, a food writer whose cookbook of classic Thai dishes will be published next year, calls the Intimidation Factor. She observes that just as many visitors to Penang shun koay teow th’ng stalls, so do tourists tend to avoid Thai wet-dry noodle shops.

“If I were a foreign visitor to Thailand … I wouldn’t know how and what to order,” she says, noting that knowledge of how a bowl of noodles is composed and what ingredients are commonly available are prerequisite to confidently customizing an order (sample instructions: “fat cellophane noodles, dry, fish balls, no crispy wonton, no beansprouts”).

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But maybe the biggest reason some dishes, no matter how well-loved on home turf, never achieve global street-food fame is rooted in an imprecise alchemy of migration and marketing. By all rights pho, a deceptively simple combination of broth, rice noodles, meat and bean sprouts, should take a back seat to a dish like bun rieu, an intoxicating crab and tomato soup featuring cloud-like “dumplings” of crab fat. But as Australian food writer and street-food tour leader Mark Lowerson points out, the large number of pho shops opened overseas by Vietnamese emigrants mean it’s “rare for a tourist to come to Vietnam not knowing or having tried it somewhere.”

The dish’s popularity overseas has even looped back to influence how Vietnamese at home advise visitors. Proud of what Mr. Lowerson describes as “Vietnam’s most renowned contribution to world cuisine,” most are likely to name pho as the top must-try dish.

There are lessons here for travelers in search of great, but underrated, street foods. First, forget what you know of the local cuisine from restaurants at home. Second, don’t be daunted by the challenge of ordering with inadequate information. Finally, don’t be fooled by appearances – they’re not always an indicator of taste.

Readers, what are your favorite under-the-radar street foods? Share your tips in the comments.

Robyn writes about food and travel. She’s lived in Hong Kong, Shanghai, Bangkok, Ho Chi Minh City and Kuala Lumpur. Two years ago she moved to Penang — for the hawker food, of course. Follow her on Twitter @EatingAsia