"Oh dear goodness, wake up right now, I'm absolutely stuffed, I-I can't hold it!"
At the break of dawn, no less. Four bowls of kibble for breakfast, one-and-a-half for lunch, and no uses of the toilet… and you're so deeply immersed in your dream that you couldn't give a damn. But your partner did. Even if you have two stomachs, all the waste exits through the same hole, and it's no wonder all the poop in your bowels are bothering your anus's sleep.
You stumble off your bed, making sure all four legs stand on the ground, and rush to the toilet as quickly as you can manage. And it hits you that you have no idea how to use the damn thing. "Just be quick would you!" You make a U-turn to face the door, walk backwards to set the lower body up on the throne with the front legs standing straight on the floor and the hind legs folded forwards, raise your tail, let go and hope for the best. Fortunately the poop nicely slides into the bowl, the moans of your partner interrupting after each turd is cut. The entire deal lasts a minute and a half or so.
"Oh you can't see this, but the turds are stacking over the water level in the U-bend… This stinks, but so, so irresistibly… The feel of the remnant on my rim feels so soothing… but are you planning on wiping me?"
"Full experience. You're the anus of a dog, and even with sentience, the extra limbs mean I need to bend very far backwards to reach you, and will require walking off the toilet bowl. It's just not worth."
"Oh yes… May that lingering aftertaste never fade."
You flush the toilet, with some water splashing on your behind. "Oh, this is soothing, like a wash or something," your asshole mused.
"You're really, really liking this, aren't you?"
"If 'this' means this experience with the toilet, absolutely, but this won't occur more than two or three times a day and I am not sure what life would be for the remaining hours, with no forms of entertainment…"
"If you need anything, just say it aloud. Remember, everyone else treats you as nothing but my body part. And don't forget the farts!"
"Oh, you."
You walk forwards with your forelegs, dragging your behind onto the floor in a sitting position, then stand it up, wash your handpaws, and walk out of the washroom.
You're not sure how you could use this weekend well.