There is not enough humour on here!
A man goes to the doctors for a check up, and after 30 seconds the doctor says, Keith, you are going to have to stop masturbating.
Keith says why?
The doctor says because I am trying to examine you!
That one split my sides, closely followed by
A father and son are out for a drive and the son says to his father dad, why is my sister called Teresa?
The father smiles and says, well son, your mother likes to make anagrams out of things she loves and Teresa is an anagram of Easter.
The boy ponders for a moment then the dad says, do you understand now Alan?