Why were Patrick and Susan dating in the first place?
Patrick's Catholic faith was so important to him, yet he was involved with a Jewish girl. Don't get me wrong, I've got no problem with interfaith relationships, but his character was so staunchly Catholic throughout most of the movie, that it strains plausibility that he would be involved with a girl who wasn't Catholic. Not only that, but not Christian.
It'd be one thing if it was true love and these two were head over heels for each other, but nope.
Just one of many ways these movie strained plausibility. Don't get me started on the "triangle" Barry and Audrey had with Henry, a guy who may or may not have existed.