You could say it's much in the vein of earlier Pok?mon, like Rotom: inanimate objects that are somehow Pok?mon (much to the dismay of folks who think Pok?mon designs are getting less creative). Or, more broadly, it continues the type of Pok?mon that are seemingly based on Tsukumogami—"animate houshold objects" according to Wikipedia. The way it's supposed to work is, after a lifetime of service, tools and instruments gain souls and become alive. Hijinks ensue from there...which might explain why Klefki has an ability called "Prankster." Tsukumogami are a part of Japanese culture, which makes it seem like Pok?mon such as Klefki are less the result of lack of imagination at Game Freak than some people would think.
Yes, this is me defending a Pok?mon that's a keyring. Because god damn it, it's kind of ridiculous, and that's exactly what makes it notable (same thing with the ice cream cone Pok?mon, and the Pok?mon that's made of garbage). Meanwhile, you look back at, like, the original 3 starters and they're just a bunch of turtles. Turtles! Dude. C'mon. Stuff like that can't be the standard to which we hold other Pok?mon to!
Well, regardless of whether or not you take its design seriously, you probably will take its battle prowess seriously. Some of the tougher trainers in X & Y have a Klefki, and it's fully capable of wrecking your ****. The first time I went up against one, that's what happened. I almost got destroyed. Hence, I suppose, memes like this one posted by foolishfox on Reddit: