Gabe Kaplan evidently wishes he were Jerry Seinfeld - a stand-up comedian who finds himself in the title role of a 30-minute situational comedy. Only Seinfeld did it better, and with more taste.
Welcome Back Kotter has some legitimately comical themes - the teacher who comes back to his old school is a nice touch, along with the improbable scenes that the most underachieving class in the city would enjoy spending time at their teacher's apartment. But it makes inappropriate light of a serious sitation in our society: the underachieving student with little likelihood of success upon graduation.
Somehow, a principal who hates a block of his students is funny. Somehow, a heartthrob actor is humorous when he can't answer his own name.
I'm embarrassed that I really do like the show. But it thrives on second-rate stand-up "uncle" jokes, the stale humor of a forged note for every occasion, the appeal of an actor who would later go on to be a national sex symbol...
... and the innocence of Arnold Horshack, his enthusiasm in knowing the answer to just one question asked in class, and his pride in his family name: "the cattle are dying."