The Papaya King has been a brightly-colored, self-hyping, hot-dog-selling fixture at the corner of 86th Street and 3rd Avenue since the 1930s. Its garish yellow-and-red storefront is covered with boasts about the health benefits of the miraculous papaya. Inside, there's a counter with a couple cash registers, six or seven stools where you can perch to eat your lunch, and thousands of enthusiastic signs promoting the fabulous qualities of papaya. And, usually, a fast-moving line of school kids, teenagers, and business people stopping in for a snack.Papaya King sells three things: fruit juices, hot dogs, and knishes. The hot dogs appear to be ordinary hot dogs; I'm a vegetarian and have never eaten one. I go for the fruit juices and the knishes.The juices come in several flavors. There's the papaya, of course, but there are also mango and a so-called banana daiquiris. (To my mind, a daiquiri must contain rum, and this drink does not. It's still good, though.) You can have these juices straight, for about $1.50 for a 16-oz paper cup, or you can have them made into a smoothie with fresh fruit, for an extravagant $2.90. The knishes come in plain or cheese. They're square packets of deep-fried mashed potato, flavored with pepper and probably some other spices and clearly a lot of butter, and they're simply delicious: the chewy golden-brown crust and the smooth interior are mysteriously satisfying, especially on a cold day.A smoothie and a knish make a satisfying lunch, or at least a hearty snack, and still leave you with change from a $5 bill. It's probably the perfect comfort food.