"Welcome Back, Kotter" is a television sitcom that aired from 1975 to 1979. The show is set in a Brooklyn high school and follows a group of underachieving students known as the Sweathogs. The main character, Mr. Gabe Kotter, played by Gabe Kaplan, is a former Sweathog who returns to teach at the school and help his students succeed. The series is known for its humor and memorable catchphrases, particularly from the character Vinnie Barbarino, portrayed by John Travolta. The show addresses themes of education, friendship, and the challenges faced by both teachers and students in a diverse classroom setting.