Downplayed: Bob attends a class on basic military strategy in the morning, just before the talking mongoose attack. It didn't explain specific tactics for that situation, but was still useful.
Talking mongooses are really dangerous and attack often, especially in the current season; of course there will be a lecture about defeating them.
The professors can see the future, and only give lectures about dealing with attacks that will come later that day.
Inverted: Bob defeats talking mongooses through sheer ingenuity, because there is no book about defeating talking mongooses. The next day he gives a lecture about dealing with those funny and vicious animals.
Subverted: Bob tries to use the information he learned in the lecture to defeat the talking mongooses, but it doesn't work.
Double Subverted: ...because Bob didn't pay enough attention in the class. An Aesop!
Parodied: The professor of Talking Animal Attacks 101 is a complete and total loony, suggesting the use of duct tape engineering to defeat talking mongooses. His methods, and only his methods, work.
Zig Zagged: Bob is using the knowledge he learned earlier in class to defeat the talking mongoose. The teacher shows up and tells Bob he is doing it all wrong; he actually was day dreaming in class and thought up a completely different way to defeat the monster which wouldn't work. Fortunately, he's not fighting a real talking mongoose, but rather an evil alien disguised as one, and his day dream was actually a vision granted by a good alien on how to defeat his current foe. Will Bob make the right decision and trust his day dream over the teachers word?
Bob isn't in education in any sense.
Bob's area of study is unrelated to fighting evil, and none of the information helps him in this regard.
Enforced: This trope is a somewhat Anvilicious way about delivering the aesop of listening to your teachers.
Lampshaded: "Hey look! A vicious talking mongoose! It looks exactly like the one in Professor Clayton's class this morning!"
Invoked: Bob forces himself to stay awake during Professor Clayton's extremely boring lectures. It can save his life!