When Screech gets thrown in detention, he was wearing a long sleeved striped shirt and blue pants, but in his next scene after Zack sneaks out of detention, he was wearing a white T-shirt, red pants and a multi-colored jacket.
Mr. Belding confiscated Zack's phone, but not his radio. Mr. Belding should have confiscated Zack's phone AND radio.
When Tori calls Zack's phone, Mr. Belding assumes it's Zack's mom, all from her saying "Hi. Mr. Belding?" She doesn't state who she is at all.
Ken Kelly says that caller number 10 will get the chance to win a trip to Hawaii, but Zack prevents anyone else but him from being able to get a call through, making Zack caller number 1 and thus not the caller who should have been eligible to participate in the trivia contest to win the grand prize trip to Hawaii.