Testing object literal as prototype:
x + y = 1 (original)
x - y = -1 (original)
x + y = 1 (original)
x - y = -1 (original)
x + y = 1 (original)
x - y = -1 (overwritten)
x + y = 1 (overwritten)
x - y = -1 (overwritten)
x + y = 1 (original)
x - y = -1 (original)
x + y = 1 (original)
x - y = -1 (original)
x + y = 1 (original)
x - y = -1 (overwritten)

Testing the String prototype:
s.identity() = I'm a string, I believe.
s.indexOf("s") = 6
s.identity() = I'm a string, I believe.
s.indexOf("s") = 6
s.identity() = I'm a string, I believe.
s.indexOf("s") = -1
s.identity() = To me you're just a number.
s.indexOf("s") = -1

Testing the global object as prototype:
globalFixedFunction1: original
globalFixedFunction2: original
globalFixedFunction1: original
globalFixedFunction2: original
globalFixedFunction1: overwritten
globalFixedFunction2: overwritten