Get something really comfortable, a shirt, sweatshirt, sweater. Anything you can sew on.
I grabbed one of my dorm's
logo "burning man" sweatshirts,
but I painted over the silkscreened logo so it would just be a plain black sweatshirt.
You can sort of still see it in the photo.
For a little extra brio, I added the instructions for how to use a breadboard sweatshirt, as a pun-couplet on the back, using just a paintbrush and some bleach.
Check out Alex's bleach dyeing
instructable to see how I did that.
My major (Electrical Engineering and Computer Science, Course 6) produces an unfunny yet punny shirt every year. Walking around MIT's campus, you notice students wearing, "Six Hertz" shirts. Meaning either "(Course) Six Hurts" ('cause there's a whole lotta work), or an electronic signal frequency specification.
I thought I could do much better in terms of EECS related puns (and why should school "hurt"? I don't wanna wear a shirt that says that), so I wrote "Socket to me" on the back, in response.