Paige: ...he could just zap them onto a roof like Harry Potter would or something.
Piper: After seeing what the kid can do inside the womb, he's no Muggle.
Phoebe: Hey, what about Potter? Potter Halliwell?
Leo: ...that's why I'm gonna say no to Po...
The four of them are making references to the popular "Harry Potter" book series by J.K. Rowling, later developed into a series of films. Harry is a young wizard who, when he was young, would mysteriously have the things he wanted to happen do so. His last name, Potter is a suggestion made as a P name for the baby. A Muggle is the term Rowling gives to the people in her books who have no magic in them.