You can hide an ATtiny85 inside a SNES extension cable. With a mini-din 8 on the other end, it converts SNES controller to CD-i using the SNEStoCDi Arduino project

The SNES2CDi adapter remains a popular piece of CD-i hardware that people want to buy or create. CD-i member Simon Laroche made another improvement by hiding the tiny-arduino inside the SNES plug of a SNES extension cable. In this way, you don't need an extra 'block' that holds the arduino system. Simon: "I hid an ATtiny85 inside a SNES extension cable. With a mini-din 8 on the other end, it converts SNES controller to CD-i using the SNEStoCDi Arduino project. It was a very tight fit, and I never want to do this again. But it turned out great, looks perfect from the outside." We are still gathering interest who wants a SNES CD-i Adapter and who can make one, we have over 10 CD-i members willing to play 40 euro each. Join the community and share your CD-i interest!