I suppose the Casio SA-8 is barely above a toy (no jack out, no MIDI, tiny basic keyboard, limited sound), but I circuit bent mine. Is anybody interested in bending on this forum?
Here is my Circuit Bent Casio SA-8. I am using it on a real track - Vive la Difference - in conjunction with real synths and real guitars + real bass.

The additions are - from memory, so may contain minor errors - as follows:
Top Row: Jack out, Volume Knob, Reset button, Internal Speaker on/off, Power Led, 6V power in
Second Row: Feedback Knob, Feedback Amount, 5th (on/off/on), Distortion, Distortion Knob, Glitch, Glitch Knob
Third Row: Cowbell (extra sound), Extra demo 1, Extra Demo 2, Extra Demo 3 (currently incorrectly wired?)
Fourth Row: Hidden sound buttons (allows 100 sounds in conjunction with pre-existing blue buttons - instead of just 25)