The Build

The plug is 3D printed in PLA, carefully sanded, and coated with multiple layers of UV resin (a technique I've perfected after making many other "adult toys" - buttplugs included).

The extended base sits between the cheeks and houses two modified laser modules from AliExpress:
A surprisingly powerful green laser and a red laser upgraded with a stronger diode salvaged from a DVD-RW drive.

Both beams are split into dozens of rays and reflected downward at 45deg via small mirrors, creating a bright laser "tail" on the floor behind me - like some kind of cybernetic demon peacock.
For the fog effect I built a custom vaporizer (0.5Ω coil, 4 ml glass tank, small fan) running 50/50 propylene glycol / vegetable glycerin.

The whole system is controlled by an STM32F051K6 that handles multiple laser blinking patterns, smart heater temperature ramping, and PWM via MOSFET - like a proper embedded gentleman. 
Power comes from two fat 26650 5Ah Li-ion cells in parallel, carried in a small pouch on the belt together with the electronics and fog system.

Connection to the plug is via USB-C cable (although no actual USB protocol was used here, just cable and connectors) + silicone tubing for the fog.

Remote control is done wirelessly with a foot switch hidden in my shoe. The confused and delighted reactions when people realized I was controlling everything without hands were pure gold.

Legacy

The device was so well received that I took it out to a few more parties afterwards. Nowadays when I show up at local kink/fetish events, people literally yell "Laser Butt Guy!" and similar cheers. I have never been more proud.

Safety & Sanity (yes, I still have both eyes)

Despite the absurd concept, safety was taken seriously. I've built 405 nm laser cutters/engravers, full RGB party scanners, and other laser projects before, so I'm not completely insane.

The plug itself contains only the laser diodes and optics - everything else (power, electronics, vaporizer) lives safely in the belt pouch. I'm not crazy enough to put Li-ion cells... elsewhere.

The beams are heavily diffused and poorly collimated (~10 mm spot at 3 m). In normal use they point at the floor. Brief sweeps across a crowd that was already dancing under strobes and club lasers? Acceptably irresponsible.

Note

I'm fully aware this project is... unconventional. Because of that, I'm starting with this overview.

If the initial reaction here isn't too violently negative, I'll follow up in a few days with full technical details, CAD cross-section, some photos, and maybe even a short video.

And I'll try to keep it as SFW as possible ;)