Zack Morris - classic ESTP
Kelly Kapowski - ISFJ
Lisa Turtle - ESFP
Screech Powers - defintiely NP, probably iNFP
A.C. Slater - ESTP but ISTP is possible
Jessie Spano - ENFJ
A lot the typings seem to be based on false stereotypes, like Zach being too manipulative and having too much vision to be a ESP.