Within a neighbourhood you usually open one house and all the others and their occupants are “paused” mid-activity. However Sims from the “paused” houses can randomly visit the one you have open without breaking the continuity of their own household.

E.g. you leave one house with the sim in the shower, go play a different house and hey presto the sim that was in the shower comes to visit. You then switch back to the other house and the sim is still in the shower.

So the murder clown would be paused in his house doing nothing yet still be making cameo visits around the neighbourhood.