I was inspired by the cowbell SNL skit, as well as my husbands usage of his cowbell app during the Winter Olympics to create this T-shirt for him. Jessica, from Running with Scissors, has done many projects using the freezer paper method, and has a great tutorial on how to do it. It might be a little confusing your first time, but after that, it's a cinch. I've used freezer paper only once for another project, so I had some on hand, but you can find it at fabric or quilt shops.
I chose a font on Word, enlarged it, then printed it out. I made the cowbell myself drawing it freehand. Then I traced my pattern onto the paper side of the freezer paper and cut it out using an exacto knife.
Once cut, I positioned it on the T-shirt and ironed it on. Freezer paper is awesome.
Then I painted. I used two coats, letting it dry a couple hours in between. The freezer paper creates the perfect seal to keep the paint just where you want it, then peels off easily once you're finished.
Here it is finished. When my husband saw it, he asked me where I bought it from (ha!). He was surprised I had made it myself. Freezer paper and fabric paint are inexpensive and the possibilities really are endless, you can create any design you want and then paint it onto any fabric surface you like - tees, onesies, backpacks, hand towels, etc. Use the link above to see Jessica's full tutorial to make your own.