"Y-y-you, asshole... I no s-shhhlpbpblt..." You manage to barely stammer out a sentence before a nasty fart interrupting your unintelligent words and filling your mouth with the fresh taste of the contents of this dog's bowels. Your intelligence having dipped low in the double digits, you only had a basic understanding of things. There were faint recollections of what you were before, but they felt more like dreams than anything. Before even that however? Nothing.
The genie pats your head, or rather, the poodle's ass, an evil smile on his face. "That's right! You do know shit! In fact, it's all you'll ever know from now on. You get to enjoy every steaming turd that passes through your mouth, and all the foulness that entails. All you exist to do now is to expel this dog's filthy waste, that's your purpose now~"
The genie spoke with sick delight, clearly reveling in your miserable fate. He began to vanish in a plume of smoke, still rubbing your unfortunate predicament in your face. "Well, it was fun while it lasted human. I do hope you enjoy your new life, I think it rather suits you well~"
"W-wuh, wait, I-..." The smoke pauses, the genie almost ready to vanish once more, but now curious to hear what protests your dulled mind could possibly muster. Maybe there was enough left of your mind to put together a helpful wish?
But it quickly turns out to be nothing but a false alarm, as any possibility of a compelling argument or even any begging to be changed back is wiped out as your mouth stretches wide open. The pressure behind your mouth increases, a rancid taste growing in your mouth and getting more intense by the second. A fat log of poodle shit pushes its way past your black (anal) lips, evoking a noise from you that sounds split between a drawn-out, bassy fart and a sexual moan of pleasure. Two more thick turds slip out from the back of your "throat", squelching as they leave dark brown skidmarks along the puckered ring that is your anus-mouth like the world's foulest lipstick. With one last push from the poodle, one more heady plume of gas billows out of you, the animal now finished and allowing you to speak once more.
"...I poo-poo," You finish contently, happy to fulfill your new purpose. You'd smile if your shitstained pucker of a mouth would allow you to. The tiger genie, meanwhile, laughs maniacally at the display, wiping a tear from his eye. "Oh, how pathetic!" he chuckles, before vanishing off to likely torment another poor soul (or reward one that managed to be wiser than you), leaving you to your disgusting fate. It was probably a good thing that you'd lost most of your intelligence. Understanding the whole of your situation would likely leave you loathing your existence with every fiber of your being... But at the same time, you'd also probably have been smart enough to wish yourself back to normal. Instead, this was your new normal. You were permanently stuck as this dog's dumb, filthy anus. The only things to keep you company from now on would be the flies that crave your shit as much as you do, the noses of other dogs, and maybe even a cock or two on rare occasions. You were nothing now, but the shit-spewing, mentally deficient butthole of a poodle now, and that was how you would stay.