I have had a 4-6 month old kitten for almost 2 weeks. She is adorable and gets along with my other cat. Last night she peed on a cushion that was on the floor. My last cat would sit on that cushion, but with piles of paper on it. The urine went all the way through the carpet. All other times she pees and poops in her box.

Any ideas?

Dear Denicegrant,
I would consider myself somewhat an expert with cats I did a lot of volenteer work at a humaine society near my house, I would like some more information about your pets before I can come up with a clear answer. I would like to know the gender of both animals as well as if the litter box is kept in the same area or if it has been movie or altered in anyway. Sometimes as a kitten learns to use a litter box it can become picky about where it is or what type of litter you have. Like when you don't like the rougher toilet paper. I think that I could enlighten you on more stuff if you could please let me know some more information.
~Metal

When you acquire a new pet you should always take them to the vet for a general checkup within the first few days.
If you haven't already, now is a perfect time. While this may be behavioural and because of the stress of being in a new home or something else... it's always best and we always recommend you rule out something like a urinary tract infection first.
Your other cat is using the litter fine? Are you SURE it is the new cat? Sometimes when you get a new pet when you have one already, they may get their nose out of joint, even if they act fine around you. Is it possible your older cat may be doing it?

Also - how often do you clean your litterbox? More to the point, do you recall if it was clean at the time the accident happened? Some cats are very picky with litterboxes, and will urinate or defecate elsewhere if it is too dirty for them. (and for some cats, that's not a lot!)

Do check in at the vet first as Sariss suggested. But a behavioral possibility: trying to mark where the other cat was sitting.

I have a cat who is doing this sort of thing. She IS very picky about the litter box and I have to stay on top of that, but she is also peeing places that are kind of the other cat's territory. (Mostly places where he tends to hang out with me.) Yours may be having the same sort of issue going on.