I've had two cats over the years that suddenly started fetching as kittens. The behavior in one lasted about a year. In another (current cat) it continues, thou

I've had two cats over the years that suddenly started fetching as kittens. The behavior in one lasted about a year. In another (current cat) it continues, though less often (he's 3.5yrs old now). In both cases the behavior seemed to emerge spontaneously - we never taught them to do it and never offered any treats for doing it. They'll bring a favorite cat toy and lay it down near me and then I throw it and the process repeats sometimes for quite a while. The current cat will sometimes get quite insistent for the toy to be thrown. He seems to get a kick out of the chase.