Here's the joke involving Peggy....
A young Phil Mitchell comes home from a long day looking like a potato at school with a writing assignment. He asks his father for help. "Dad, can you tell me the difference between potential and reality?"
His father looks up, thoughtfully, and then says, "I'll demonstrate. Go ask your mother if she would sleep with George Clooney for a million pounds. Then go ask your sister if she would sleep with Brad Pitt for a million pounds. Then come back and tell me what you've learned."
The kid is puzzled, but decides to ask his mother (who just happens to be Peggy Mitchell).
"Mum, if someone gave you a million pounds, would you sleep with George Clooney?"
"Don't tell your father, but yes, I would."
He then goes to his sister's room. His sister, by the way, looked just like a young Peggy Mitchell.
"Sis, if someone gave you a million pounds, would you sleep with Brad Pitt?"
She replies, "Omigod! Definitely!"
The kid goes back to his father.
"Dad, I think I've figured it out. Potentially, we are sitting on two million quid, but in reality, we are living with two sluts. One of who'm is Peggy Mitchell, and the other one is a younger version."