There were nice mentions and throwbacks to the old series, in Showdown Zack told Mac and Daisy about all the things he did in Bayside, as did Kelly. In the 2nd season Let the games begin Zack told Mac he lived in Indiana and then Bayside (when the series started out as Good Morning Miss. Bliss), and he did a time out and broke the 4th wall. He did not do that in years.

Not to mention when they reminisced about Screech, and that he became the 1st Mr. Miss. Bayside.