...When you call the fish you named in the Science Lab by their LOTR names instead of their real ones, and your teacher gets really confuzzled.
...When you write a compare and contrast paper on the differances between Frodo and Gollum/Smeagol.
...When you frined proofreads said paper, she says I know too much about LOTR. (You can never know too much!
The paper wasn't exactly a work of art either. Someone who had only seen the movies could probably understand some, accept for some mentions of Mandos's halls)
EDIT: 10 more posts and I'm a wight! Yay!