Who played A.C. Slater in 'Saved by the Bell'?

Who played Cosmo Kramer in 'Seinfeld'? Who played Newman in 'Seinfeld'? In which TV series is Newman a main character? Who played Zack Morris in 'Saved by the Bell'? In which TV series is A.C. Slater a main character? Who played Kelly Kapowski in 'Saved by the Bell'? In which TV series is Kelly Kapowski a main character? Who played Screech Powers in 'Saved by the Bell'?