Fun with friction!
Felt and fleece work really well when it comes to adhering to other materials using friction alone. This is a great, quick science lesson to hypotheses about what will and won't stick vertically on things. Would the pillow stick to the wall? What about a heavier pillow? Would silky objects stick to the couch? Would silky objects stick to the wall? What if the materials were wet? Experiment and have some fun!
What can you stick to the back of your couch?