In the post-ending credits scene for Lawnmower Dog, Scary Glenn replaced the old professor as the new teacher in the class. He was a totally chill, laid-back guy who didn't actually teach the kids anything. He was way more spiritual and taught the kids only about "how to chill". He also perferred the students address him by his first name instead of Mr. Johnson. This was great for the students in the class, including Rick Sanchez and Scary Terry, who were sitting back in their chairs and smoking weed.
Scary Glenn has a receding hairline with large dark grey hair and matching beard, sporting a hippie-style shirt and necklace. He also happens to be the only scary person who doesn't have miniature swords for fingers.
Scary Glenn has a more relaxed approach to teaching than his predecessor, insisting his students call him by his first name and using bongo drums in class (saying that the students can't learn anything until they learn how to chill).