Because of Peter is a man who is weighty color gently friend before, he has a fat lot of any male friends. Peter feels embarrassed and gives himself a mission to find male friends. So one of the reasons why Peter and Sydney become good friends is Sydney appearers on time.
They meet in Sydney's open house. Peter finds that Sydney is a person who is decadent, incorrigible, and crazy. But actually, Sydney also is very kind, accommodating and candid. Because of the character Sydney has, Peter likes to be a good friend with him.
Day after day, they see a great deal. They sing songs together, walk in the park, and ride motorcycles. In my opponion,they develop a friendship very quickly during this time. So, there is no doubt that thay will became a good friends.