One even made it to the pillow:
I cut them out of various cotton fabric bits to spice up a very boring blue/white striped cover. I glued them on with Vliesofix, for me the easiest way to fix parts for applications. They can stay fix even when you're washing them, but I don't want the fishes to fray, so I framed them with small zigzag-stitches. The eyes and the bubbles I fixed by quilting about 3 times around.
This is me on the living-room floor fixing the pieces with the pressing iron.