Danny and Joey discover that their high school girlfriend was using them to make Jesse jealous. It has previously been stated several times that Jesse is 6-7 years younger than Danny and Joey. If they and their girlfriend were 14-18 years old, Jesse would have been 7-12 years old.
Becky mentions to Michelle and Denise while looking at Becky's wedding album that her dad was "really nervous" when arriving at the church, but in "The Wedding: Pt. 2" it was actually Becky arriving at the church after bailing out Jesse from jail.
During the scene when Michelle and Steve are getting married, Denise tells Steve to go stand by Michelle. You can see that he's wearing a watch. Then after he's standing next to Michelle, his watch is gone.
When Michelle comes into the kitchen and sees the cookies, Steve starts to put icing on one of them. It then cuts to a close-up of Michelle, and the icing tube is now further from the tray and nothing is coming out of it.
Just after Jesse discovers his file has been erased, Alex's left arm hangs at his side. In the next shot, the arm is raised and he's pointing at the computer screen.
Stephanie says to DJ, "I thought you'd be the first to get married." In Middle Age Crazy Stephanie was going to marry Harry.
When Denise calls for everyone to take their places for the pretend wedding, she calls Steve "the husband." Since the wedding hasn't actually taken place yet, he'd be the "groom."