The local Hawaiian-style food item which is on the menu at McDonald’s is saimin. It is a noodle soup dish (ramen) which was developed by different immigrant groups in Hawaii. Saimin was inspired by Japanese ramen, Chinese mein, and Filipino pancit.

Saimin is a soup dish that consists of soft wheat egg noodles served in hot dashi garnished with green onions. It is mostly like ramen, the same noodle soup dish found in Japan. In Hawaii at McDonald’s, it is made fresh with thin white noodles in a clear broth with green onions. It is often served with kamaboko (fish cakes) and sometimes ham or char siu (pork). It is most often eaten at lunch time.

In the late 1960s, Maurice J. "Sully" Sullivan, an Hawaii entrepreneur and owner of the first McDonald's restaurant in Hawaii convinced executives from the McDonald's corporation to expand McDonald's menu to include a local "ethnic" food. Once proper research had been done a recipe for McDonald's in Hawaii to add saimin as a menu item was developed. Saimin was soon offered to the public; it at once became a tremendously popular item at the restaurant chain.

More Info: en.wikipedia.org