The opening scene when the gang's at the table, Max brings the food: one plate to Kelly, one to Screech, and one to Slater who slides his over to Jessie. In some shots, though, Screech no longer has a plate and Slater does.
After Mr. Belding leaves his office after talking to Slater, he came out from the opposite entrance of the hallway where his office wasn't when he walked in on Zack selling Lisa's clothes.
Mr Belding's story on how he met his wife in college through the swim team contradicts his story in "Good Morning Miss Bliss," where he says their retainers got stuck together while they were bobbing for apples in high school.
Lisa uses her Father's credit card to buy several outfits. No store would allow someone who is obviously not the cardholder to use the credit card.