Hello. A mysterious object from a 'Mr. Macguffin' has recently been given to you. Maybe it's a remote, maybe it's just a pretty rock. Maybe a pendant. What it is doesn't really matter. What will matter is what it does. This small object, while un-extraordinary in appearance, has the power to alter reality... but only in a very precise way. Simply put, any human (and ONLY HUMANS) that this is used on, will be retroactively become a humanoid lion person, and also a nudist.
Paw pads will be tough enough to deal with things like needles and broken glass. Also, women will be 'bald' lionesses, while males will all gain a full mane. Social habits will also change as well. This thankfully does NOT include the male lion's instinct to eat any lion cub that isn't his own, but it does include the harem mentality, where several females are mated to one male. Naturally, this means that a large percentage of any single male who is changed by this method WILL become a female. All memories, and historical records were retroactively transform, meaning that if you went back in time, you'd find them as lion people in the past as well. Those transformed will be usually in exceptional shape. And a powerful sense of community.
If this object is not used, or kept with the intention of not using it, or 'intention of using it so it'll not vanish so it won't be used by someone else' it'll vanish and appear to someone who will use it, and is indestructible. Now what kind of world of lion people nudist will you make?