Genitals Strange Genital

That's what a guinea pig penis looks like. They're called prongs.

Thanks for that. I have only had guinea pigs since January and never noticed it before. Is it ok for it not to fully retract inside the body?

Well, they do usually retract fully. Is your pig older, or overweight?

Some male pigs develop problems where their penises do not fully retract, and require lubrication around the shaft to help it slide back in better. I've even read of a case where the penis completely failed to retract, and the vet put in some stitches across the end of the sheath to keep it from coming out any more than was needed for the pig to urinate. But that was a pretty drastic case.

I'd check him carefully and make sure there's nothing inside the sheath that is causing him pain or keeping the penis from retracting. You can get some pretty gross stuff out of there, and may have to start cleaning him on a regular basis.

Boars tend to get smegma, dried semen, hair, hay, and other foreign objects stuck in the prepuce, making it impossible to retract the penis. I would extend the penis carefully, gently remove anything that shouldn't be there, apply a thin coat of lubricant (plain old KY jelly will work fine and is available at drugstores), and put his penis back in. He will be traumatized, of course.