This is basically the case for a lot of events. Smoke rings, enemies, and the like would show up as other, weird stuff like black vines, jj2 logos and the like unless there is a sprite of them already in the level (i.e a Caterpillar in the level, or a trigger rock with a generator would prevent smoke rings coming out from crates to look like floating jazzes, and Doggy Dogs placed in levels would prevent the other Doggy Dogs placed in crates to just not appear).