glowing in the wrong place

I was five when my parents bought me one of these:
















It's a glo-worm. This little guy wears a night cap and his head lights up when you squeeze him. But I just watched BBC's Planet Earth, and turns out that real glow worms don't actually wear jammies and their heads don't light up. Glowing goes more like this:


















I guess I can see why Playskool took a few liberties. I don't see too many parents buying Glo-worms for their toddlers with this catchphrase on the box:

"Squeeze me and my butt lights up!"