In this question, we are asked to identify the incorrectly matched pair. Let`s analyze each option to determine the correct answer.

Option 1: China Sea and Typhoons. This pair is correctly matched. The China Sea is prone to typhoons, which are tropical cyclones that are common in the western North Pacific Ocean.

Option 2: Gulf of Mexico and Hurricanes. This pair is correctly matched. The Gulf of Mexico is known for its susceptibility to hurricanes, which are intense tropical cyclones that form over warm ocean waters.

Option 3: North-West Australia and Willy Willies. This pair is correctly matched. Willy Willies are an Australian term for tropical cyclones or whirlwinds that occur in the north-western regions of Australia.

Option 4: Indian Ocean and Tornadoes. This pair is not correctly matched. Tornadoes are more commonly associated with regions such as the central United States, known as "Tornado Alley." While tropical cyclones can form in the Indian Ocean, tornadoes are not typically associated with this region.

Therefore, the correct answer is option 4: Indian Ocean and Tornadoes.