You can't resist the urge to begin stroking your cock. You pull at it with your right hand. Is it just you or does if feel bigger than normal? Whatever. You'll use both hands. Stroking with both hands, you watch as your dick starts to get darker.
"What's happening?" you gasp between moans.
Unable to stop you watch as your dick lengthens with every stroke. Soon your previously 6-in boner has doubled in size. It's gotten darker now, too, almost black. You know you should be scared, but all you can feel is immense pleasure. Your cock head begins to flatten, but you keep stroking. You notice that a layer of skin has joined the base of your cock to your body and enveloped your cock like a sheath.
You notice other changes are moving across your body. This hair is spreading from your previously trimmed pubes, and it's moving across your hips, your legs, and your belly. It travels down to your feet, which are getting longer. You feel the urge to stand on your tiptoes. You're still stroking your big dick, unable to stop, as your toenails darken and merge. HOOVES. You have HOOVES. You have FUR. You have a DONKEY dick. You've recognized it now.
Suddenly you feel another pain in your ass. No, not the dildo, which is still moving back and forth of its own accord. It's above the dildo. You turn to look at your butt and you see a lump forming above your butt cheeks. As you watch it explodes outward into...a TAIL! A DONKEY TAIL!
You know you should be panicking by now, but it just feels so amazing! You continue stroking yourself as your neck lengthens and your face cracks, pushing outward into that of a donkey. Your ears are getting longer and the fur has spread all over your body, not an inch left uncovered.
You feel yourself building to climax as the dildo pumps faster and harder. It empties a load of its magic cum into your bowels as your own load shoots forth from your throbbing cock!
"HEEHAW!" you bray. The dildo drops from your ass onto the floor, cold and unmoving.
You look at yourself. You're a male anthro donkey.
Suddenly...