Someone just walked into the restaurant i work at, dumped this soaking wet kitten in the lobby, and left without saying a word. I just got a kitten this month, so i took her home with me since i have kitten supplies and everyone else at work has too many pets.
She cried the whole ride home, and my kitten (13 weeks old), Niniane was not happy about the new cat. I took the stray into the bathroom and fed her. Afterwards i weighed her and she wasn't even 2lbs. She was absolutely filthy, so i gave her a quick bath without much struggle.
I dried her off and groomed her with the slicker brush and then let Niniane into the bathroom so they could socialize a bit. Nini was curious, but very standoffish and mostly just hissed while the stray just wanted to climb into my lap. I put a cat hammock, scratching post, and some toys in the bathroom (none of which Nini uses) and have locked the stray in there until i know she is litter trained. Currently she is jist sleeping in the hammock, so i think I'll leave her there for the night and try to socialize the kittens some more tomorrow.
Edit: i think i am gonna call her Boudica. It's much better than "the stray". She just peed in the litter box and even buried it, so that's a massive step. Unfortunately I'm still gonna keep her in in the bathroom for the next few days, but I'm so glad she used the litter box.
Keep them apart for a week or so if you can to let any incubating infections show up. I recently had an upsetting experience with a family of stray kittens and their mother that my wife and I rescued, only to find out that they had feline parvovirus and had to be euthanised (whilst the kittens seemed fine when we caught them, the prognosis for kittens with parvo is horrendous; even the mother only had a 50/50 chance of survival). We kept them separate from our cats (and they are vaccinated anyway), but we still had to bleach the bathroom almost to oblivion to kill any trace of parvo. It was just a horrible situation.