2x19 - Full House

In college, Joey had a girlfriend named Patty Fogerty, who ended up leaving him for a guy named Michael Winchester. This left Joey devastated, because he wanted to marry her. Now, years later, Patty tracks down Joey's phone number and calls him. Joey invites Patty over to the house. Danny doesn't like this, because he doesn't want to see Joey, once again, get hurt by Patty.