Aww, poor Harley! It's not that he's scooting on the bed per se - that's what Maggie does on the floor even though there's usually nothing there (and she's always done it, for the almost ten years we've been together, she just likes her carpet toilet paper). He either gets up here to clean and is in that sitting up position licking his paws or his belleh and so his butt is RIGHT on the bed as he shifts around, or it's just so poopy that even him sitting or lying down leaves a streak. >.< I had to pick another dingleberry off his arse this morning that was just hanging there.
I wish he could be less poopy butted too, but it's generally just how he is. I mean, it's worse when he eats Maggie's kibble (that he's allergic to), but even when he hasn't gotten into anything, he's always just left nuclear warfare in the litterbox. I could weaponize Yuan's poo. I'm surprised Homeland Security doesn't think I'm building biological cat poo weapons. XD
When he first came home with me, he came from the shelter with a giardia infection that took four rounds of antibiotics to clear up and during the final round, me cleaning his butt every day with soap and water or wet wipes because he was reinfecting himself by cleaning it. It took me a while to figure out that him being stinky was just part and partial after that because I kept thinking he was still infected! So even when he was young and flexible enough to reach - yeah, Yuan poops hazardous things from the bog of eternal stench. XD