A friend of mine told the following  to me. Just for fun's sake. Nothing personal. 

Who said Allah is God? Muhammad said! 
Who said that Muhammad is the messenger of Allah? Muhammad said!
Is Quran God-given? Who said? Muhammad said!
From where was acquired the matter in Quran? From Jibreel! And who said that? Muhmmad said!
Who is Jibreel? An angel of Allah! And who said that? Muhammad said!
Who said to believe firmly in Quran? Allah said! And who said that? Muhammad said!
Did Muhammad see Jibreel? Who told? Muhammad said!








What if what Muhammad lied? Muhammad does not lie.
Who said? Muhammad said.


This said, another thing is that nobody takes pain to check whether Muhammad was right or wrong. Simply jesting is very easy.