Simpsons Comics #217

Homer accidentally invents the most powerful vacuum cleaner on Earth and teams up with door-to-door salesman Gil Gunderson to peddle his wares. Meanwhile, when Bart and his pals get in trouble and are assigned to help out Groundskeeper Willie, the school handyman has enough extra time on his hands to earn his GED and teacher's credential. In no time, he becomes Springfield Elementary's most sought after substitute teacher.