I hear he was totally a*** on the set
I hear everybody got along with mr Sourpuss Mr Woodman
I went to a taping of Welcome Back Kotter, and the main thing I remember is the introductions before the taping began. Each Sweathog was announced and came onstage except for John Travolta. Then the announcer said, "And now...the handsome heartthrob you've all been dying to see!" The audience went nuts, thinking Travolta was about to come out. Instead, the man who played Mr. Woodman strutted out, proudly smiling and waving! I suspect the guy had a great sense of humor.
As for Gabe Kaplan, I knew a girl who worked with him after "Kotter" was canceled and had absolutely nothing good to say about him.