The McCrispy is defined by the geometry of its fillet: it is flat and wide rather than thick and craggy, and the build is engineered around that flatness. A fried chicken sandwich usually leans on a lumpy, irregular coating for its texture, with the bun's job being to keep that craggy shell from steaming soft. This one runs a single even-thickness breaded breast fillet pressed broad enough to reach the edges of the bun, so the structural problem is not protecting a thick knob of crust but keeping a thin, wide sheet of it crisp across its whole span. The fillet is the architecture; the rest of the sandwich is arranged to keep that flat plane from going limp.
The craft is in the even cook and the dry build. A flat fillet of consistent thickness cooks through before the coating darkens too far, which is the trade the shape buys: less juicy mass than a thick cutlet, but a crust that stays crisp edge to edge instead of soft in the middle. The breading is applied for a fine, even crunch rather than a heavily clustered one, because the point of this build is uniformity across the width, not a rugged surface. The sandwich is kept deliberately spare: crisp pickle slices and a smear of butter or a thin sauce on the bun, with nothing wet poured over the fillet itself, so the coating meets no moisture until the bite. The carrier is a soft, faintly sweet toasted potato roll, toasted on the cut faces specifically so a warm, slightly crisped bread surface sits against the fried plane rather than a cold soft one steaming it down. Pickle is the only sharp, cold element, doing the acidic counter that a rich fried sheet needs, and the build is assembled to a fixed pattern so the proportions hold every time.
The variations are a matter of dressing the same flat fillet. A spicy version lacquers the coating in a pepper sauce or seasons the breading hot; a deluxe build adds lettuce, tomato, and more sauce while keeping the same fillet; the wider American fried chicken sandwich in its Nashville hot and Korean-American readings pushes the crust and the glaze much further. Each of those keeps the flat-fillet rule and changes one element, and each deserves its own article rather than being crowded in here.