Last semester a student asked me for a new copy of the Unit Circle reference sheet we were using in Trigonometry. "My dog ate my unit circle," she said, explaining it was her new puppy who had done the deed. I could gladly give her a replacement; at least this wasn't homework that was munched!
Last semester was also the first time I taught Trigonometry in - well - twelve to fifteen years. What an adventure that was! I'll let you imagine the hours of preparation I put in. I'll let you imagine me blessing the author of the textbook over certain problems. I'll let you imagine my marginal curve drawing skills put to use on sine and cosine graphs. Well, at least proving identities is fun! I think that came from the prof I originally learned trig from, love her (Thanks, Jean!). She said that she and her husband worked on identities together when they were still dating, so she really grew to love them. So I guess some of that positive energy rubbed off - on the math part, anyway.
It was nice to have a bit of a "challenge" and to review the subject I hadn't worked with for some time. If you don't use it, it will gather rust; so occasionally it's nice to clear some of that away.
And it might be a good idea to keep Unit Circles away from puppies.