As a ubm I can tell you that once you join the cult much joy and laughter will in fact leave your life as well as those around you. Some things that were previously funny to my jw (pre jw) days now must first be thought out if they are against jw rules somehow, then you can decide if it is funny enough to laugh or not. Well, by that time the joke is gone.
We (all non jw family, never been and he is the only jw anyone actually knows) however find many things to secretly giggle about or laugh later when he isn't around. Such as when he lets swear words fly, when he mistakenly does laugh at something that might be not quite jw approved or when he is a total hypocrite (as jw's are prone to) and the list goes on....