Because why not

spongebobify.py

import string

a = input('Input text to Spongebobify: ')
b = []
upper_case = False
for each in range(0, len(a)):
    if a[each] in string.ascii_letters:
        if not upper_case:
            b.append(a[each].lower())
            upper_case = True
        else:
            b.append(a[each].upper())
            upper_case = False
    else:
        b.append(a[each])

print(''.join(b))