Write a Python function that takes a string as input and returns a dictionary with the frequency count of each character in the string. The function should treat uppercase and lowercase letters as the same character (i.e., 'A' and 'a' should be considered the same). It should count both letters and special characters.

Example:

Input: "AaAa"
Output: {'a': 4}

Input: "Python Programming"
Output: {'p': 2, 'y': 1, 't': 1, 'h': 1, 'o': 2, 'n': 2, ' ': 1, 'r': 2, 'g': 2, 'a': 1, 'm': 2, 'i': 1}"

Write a Python function that takes a string as input and returns a dictionary with the frequency count of each character in the string. The function should treat uppercase and lowercase letters as the same character (i.e., 'A' and 'a' should be considered the same). It should count both letters and special characters.

Example:

Input: "AaAa"
Output: {'a': 4}

Input: "Python Programming"
Output: {'p': 2, 'y': 1, 't': 1, 'h': 1, 'o': 2, 'n': 2, ' ': 1, 'r': 2, 'g': 2, 'a': 1, 'm': 2, 'i': 1}"