You likely heard about UTSA's fake cannon. It was on wooden wheels and castors below. Anyway, note that there is a box in front of the "cannon". They would detonate the flash smoke from the box each time the "cannon" was fired.
LMAO!!!!!!!!! That soooo looks like something UL-Laugh would do.
Ready, aim, flash-smoke sparklers!!!! Maybe a Roadrunnner genie will magically appear from the smoke next time?