Humor in the Classroom

I teach 8th grade (Information Technology and Engineering) and while I admire those teachers who can act goofy with their kids, that's just not me.  However, I do still like to share my own sense of humor with the kids, just in my own more reserved way!

One of the things I like to do is post amusing posters in my room that still have a purpose.  I found this quote that I really liked on the Internet, and "made it my own" with a Grumpy Cat meme generator.  The pretty background digital paper is courtesy of The Cottage Market,

My the second week of school, my students know I love Grumpy Cat's attitude (I want to be her when I grow up!) and have a couple other signs using her in my room too and she often shows up with some of her attitude in my PowerPoint presentations or just at an odd moment on my SMARTBoard.  

How do you share yourself with your students?