Catnip was invented by time travelling mice in the year 3416 and was inserted into the timeline as a practical joke on their archrivals the cats. Unfortunately the joke backfired when lack of evolutionary pressure from the stoned cats no longer chasing mice meant that mice never developed opposable thumbs or intelligence.
Actually, electricity is caused by tiny hamsters running very very fast. Fuses therefore consist of tiny bridges - if too many hamsters try to cross the bridge at any one time, the bridge breaks and no current flows.