Pizza
Pizza demonstrates extraordinary evolutionary flexibility. The base template of dough, sauce, and cheese has spawned countless regional variations: the thin crusts of New York, the deep dishes of Chicago, the dessert pizzas of suburban chains, the vegan alternatives demanded by contemporary dietary fashion. Toppings range from the traditional mozzarella and basil to the controversial pineapple, from anchovies to artichoke hearts. Gluten-free bases accommodate the intolerant. Cauliflower crusts appease the carbohydrate-averse. Pizza bends to accommodate every preference whilst maintaining its essential identity.
Harry Potter
The Harry Potter universe has demonstrated significant capacity for extension. The core narrative has expanded into prequels, sequels, and parallel storylines. Theme parks adapt the literary experience into physical space. The Pottermore website (now Wizarding World) offers supplementary content and interactive features. Fan fiction communities produce millions of words of additional narrative. However, the canonical core remains fixed. One cannot fundamentally alter Harry's journey, add new houses to Hogwarts, or reimagine the defeat of Voldemort. Adaptation occurs around the edges rather than at the centre.