Gloworm was a cuddly toy Glow Worm made by Hasbro's Playskool that would light up when squeezed. There were a whole range of different shapes, sizes and colours of Gloworm and apparently some of the smaller ones did not light up but were 'glow-in-the-dark' painted instead.
Introduced in 1982 all the Gloworms were fairly similar in appearance though with a chubby work-like body and two stubby arms. Each Gloworm also wore a night cap and a battery was fitted inside its plush body.
I think the idea was that the Gloworm was a comforter for children who didn't like going to sleep in the dark. The Gloworms were such a success that all sorts of different spin-off products were released including story books, night lights and videos right up until the early 90s. In 1986 Playskool also released the Glo Friends - smaller plastic models of the popular Gloworm characters.