Ok, barondla, I'll post the examples this weekend. I didn't explore the creative potential, because I was really looking to use the fisheye with more reasonable ISOs indoors, hoping the quality wouldn't drop too much in the center. In actuality, quality dropped most in the center, which rendered it useless for me. So I put the card back
But you could definitely explore "toy" photography this way!
In fact, if I owned a toy wide, I'd be more likely to go that route with that lens, as it's really supposed to have more of a toy look than it does, anyway. I suspect it would be built in a similar fashion.
The challenge to whoever takes up the "fast fish" project from here is that the aperture card isn't held in place by anything other than glue. The two small pins shown are there to locate and center the card, not hold it in place. To test new aperture sizes without cutting the original, you will have to cut paper to size, create the two holes for the pins, create the aperture disc perfectly centered, and then glue it in place. That will take some time and ingenuity.