The same episode has Zack one credit short of graduation (due to dropping a class). The only way he can get it is to successfully perform in the ballet recital, but the recital is due to be canceled because of an illness among the original cast. The rest of the gang steps in to fill out the missing roles.
One episode has Kelly's dad lose his job at the plant right before prom, with her now being unable to afford to go. Zack then stages their own prom outside the gym, complete with cake, dancing, and a sign that says "Zack and Kelly's Prom" (the original prom theme, much to Belding's chagrin).
This ignores the obviousness that Zack's family is clearly wealthy enough for him to afford to buy her a ticket and dress.
The first episode of the high school years has a dance contest hosted by Casey Kasem. The first heartwarming moment occurs when Zack gives up on trying to get Kelly as his partner and instead chooses Jessie, who had been teaching him to dance.
The second involves Screech coming to Lisa's rescue. She injures her ankle and her original date dumps her, wanting to win the contest. Screech then becomes her contest partner, creates a new dance called "The Sprain" (where he and Lisa rhythmically limp around), and the pair wins the crows over, winning the contest over other finalists Zack/Jessie and Slater/Kelly.
The episode where Mr. Belding's brother Rod comes in as a substitute had one by Belding towards the kids and one by the kids towards Belding. When Rod ditches the kids' senior trip (which was changed from Mr. Belding's idea of sightseeing in a national park to Rod's idea of white water rafting) to hook up with a stewardess, Mr. Belding gives him an awesome "The Reason You Suck" Speech finishing with Mr. Belding telling Rod to get out of his school. He lies about it to protect the kids' feelings, then offers to take his place despite his lack of skills on a boat. The kids are overjoyed and thank him. Zack then reveals to Mr. Belding that he overheard everything, but tells him that while Rod may be the cooler Belding, they have the better Belding.
Mr. Belding might be the hardest on Zack but he's actually very fond of him and even names his son after Zack, who helped his wife deliver the baby when they were trapped in an elevator.