Never fails, young cat and stink bug
Now and then, usually in spring and fall I get a stink bug or 2 sneaking around in my house. If I find them, they go for a swim in the toilet.
But if my cat finds them and they have never seen one before, they play with it and discovers why I don't kill it outright. They stink!!! And it happens just about every time I get a kitten in the house for as long as I can remember. Tux did it. Tuffy did it. Socks did it. Gateway did it. Marshmallows, Tiger, Boots, Sam, Cupcake, and many more cats I've had in the past. Once they discovers the bug, they never play with it again (thankfully!)
Stripes was just playing with one that got lost trying to get outside after winter hibernation and when he accidentally bit in one, he made a fuss and ran away I guess to get water or something.
PS they really stink. Western Conifer Seed Bug is native to my area and is fairly common but usually they stay outside. My house is around 130 years old and there are a few holes that I have yet to find and plug so they come in fall to hibernate and out in spring.
PSS did I mention the bugs really stinks?