When Screech walks into Lisa's room, Lisa says, "What's in the suitcase?" Screech isn't holding a suitcase, it's a duffle bag and those two things aren't even close but they rolled through the scene with it being called a suitcase anyway.
Mr. Belding's experiment depends on some students failing the first part of the experiment (being husband and wife) in order for those students to play the children of the students who passed that first part in the second part. What would he have done if all of the students had gotten along playing husband and wife?
Mr. Belding says the kids are paired up by last name, meaning it would be alphabetical. Kelly and Zack are correctly paired (Kapowski and Morris), however, Slater and Jessie, and Screech and Lisa should not be together (Slater, Spano, Powers, and Turtle). Lisa should be with Slater, and Jessie should be with Screech.