Screech's water pistol is clearly empty during the presentation.
When Zack is complaining to Mr. Belding about Tori parking in his spot he says he's been parking there for two years, and Mr. Belding replies that there is no assigned student parking. However, in The Fight (1992), Zack says one of the best things about being a senior is reserved student parking. Either they have a lot specifically for seniors, in which case Zack couldn't have been parking in that spot for two years, or seniors get reserved spots, meaning Mr. Belding's comment about no assigned spots would be incorrect.