Zack gets off on the wrong foot with his new professor of anthropology, Professor Jeremiah Lasky. Professor Lasky pegs Zack as a smart mouth immediately and turns the tables on him by selling him a copy of the midterm before Zack realizes that he is the instructor. All the girls have crushes on Professor Lasky, while Slater is trying to gain weight so that he can wrestle in a higher weight class.

While the girls put together a male pinup calendar in order to buy a big screen TV, Zack poses as Lasky in order to date an admirer of the professor's.

Just as Zack and Kelly are getting pretty close, Kelly is accepted to the Semester on the Sea program, which involves a three-month cruise. Zack doesn't want Kelly to go, but she feels it's an opportunity she can't pass up. Zack tries to get accepted into the program as well, but none of his schemes work. He tries to get Screech to quit the program by scaring him, but that backfires and Zack impulsively makes an important decision. Meanwhile, Slater feels guilty when he sees another girl behind Alex's back and gets confronted by Leslie.

As Zack and Kelly make plans for their wedding, they get a surprise visit from their old friend, Lisa Turtle. However, since Alex and Lesley also want to be Kelly's maid of honor, the competition between the three of them ensues. Meanwhile, Slater doesn't approve of Zack's decision and turns down his offer of being the best man. Screech agrees to take his place with predictable consequences.