Unidentified: Freaky monster head pencil toppers (Oddballs?)

Sometime in the early-to-mid '90s, I went to a flea market with my parents where I came across these totally bizarro rubber monster heads. Of course I had to have them being the little weirdos they were, and I probably ended up getting all four for around a buck.

All of them are made out of soft rubber and are about an inch tall. They're totally hollow underneath like finger puppets, but I think they're actually supposed to be pencil toppers because they each have a smaller hole underneath as well, where a pencil or pen would fit.

As far as what they're called and when/how they were originally released, that's always been a mystery to me. I did recently find a blog post using one of my images, in which the author says he remembers seeing these at Walgreens as a kid in the early '90s, sold under the name "Oddballs." He says that they came two to each blister carded pack. Based on another picture he has in that post, it seems there were versions with painted details available as well, so I'm not sure if the ones I have were sold as Oddballs or something else.

In any case, they're really strange and fun, and I like how the sculptor took a weirder, more gruesome approach than what you'd typically see with these kinds of toys. In that regard they're kind of Madballs-esque, although they're distinct enough that I wouldn't go so far as to call them Madballs knockoffs.

 
Let's take a closer look at each of these four weirdos:

In the blog post I linked above, the author said this guy reminded him of a monster head from the classic arcade game Splatterhouse. I don't think I ever played Splatterhouse so I can't make the same connection, but I do love the wretched, melting thing this creature's got going on. I remember it being totally blue originally, so I'm thinking it got discolored into two-tone blue and green at some point, but I think it looks pretty awesome that way.

This pink dude's sort of dinosaur/kaiju-like, which of course makes him a winner. He also looks like the biggest badass of the bunch. Check out those teeth!

Here we have some sort of blobby amphibious thing. It looks like the most docile of these four fiends, but still creepy. I think I can see an evil grin on those gigantic lips, which are surely getting ready to suck out your soul.

Finally we have the monster head that I find to be the most disturbing. This thing is truly an abomination. It looks like some sort of cow head from hell. Get a load of those bulging eyes and that gnarly tooth protruding from those swollen lips. Gotta love it!

I've never seen any additional sculpts beyond these four, and I've always wondered if there were more. Have any of you ever come across these "Oddballs"? Can you shed any additional light on their origins, or if there were any others not shown here?