The shrimp po' boy is defined by count, not by a fillet: it is filled with a heap of small, individually fried shrimp, each its own curl of crisp coating and sweet flesh. Where a fish po' boy carries one large piece, this one carries dozens of separate morsels, so every bite is a different ratio of crust, shrimp, and bread, and the structure is a managed pile rather than a single slab. The mass of small bites is the point, and it is what gives the sandwich its particular texture and its demands.
The craft is in the fry and the dress. Shrimp are quick to overcook and turn rubbery, so they are peeled, dredged in a thin seasoned cornmeal or corn-flour coating, and dropped into hot fat for only a short pass: long enough to set a crisp shell and curl the shrimp tight, short enough that the inside stays snapping and sweet. They go onto the bread fast and in a heap, because a pile of small fried things loses its crackle the moment it sits and steams. The thin-crusted, glass-crackly New Orleans loaf earns its place precisely because it adds no moisture of its own and shatters cleanly rather than crushing the fragile fry, and because it stays light enough to eat a foot of it. Dressed means the New Orleans system applied as a counter rather than a flood: shredded lettuce, tomato, pickle, and mayonnaise, often with hot sauce or a remoulade worked in to put acid and fat against the rich coating. A po' boy shop runs the fryer hot and builds to order so the shrimp are still crackling when the loaf closes.
The variations follow the kitchen and the season. A grilled or barbecue-shrimp build abandons the fry for a buttery, peppery sauté in the same loaf; a half-and-half order pairs shrimp with fried oysters; a remoulade dress is a standing local choice. Those forms, along with the rest of the po' boy family of catfish, oyster, and roast-beef debris, are their own sandwiches and deserve their own articles rather than being crowded in here.