With Mattel's "A Bad Case Of Worms" you got a small plastic briefcase and opened it up to a pair of sticky rubbery worms. They were available in different colours. My mate had a green set. They looked more like a snake or something! If you threw them at the wall they would stick to the surface and slowly slither down in a similar way that Wacky Wall Walkers would. They could cause a little trouble, however, if they were trodden into a carpet. They also didn't go down too well with wallpaper. The adverts made out that these creatures were hideous, but honestly, how scared could you be of something that was basically plasticine?
"A Bad Case Of Worms" was claimed to be "something that you could really love", although they were also famed for being quite disgusting. If you held one in between your thumb and your forefinger and rolled them slightly, you could make the worms look like they were "wagging their tails" - great for scaring your squeamish little sister.
"A Bad Case Of Worm" came in a variety of different colours, although if you really wanted to scare the living daylights out of someone it was preferable to have a couple that looked vaguely realistic, like a nice grass green colour rather than a vibrant orange neon.