I read a fic a few months back set after Series 4 of Doctor Who. Donna travels to America and meets the Winchester boys. She somehow remembers the Doctor, and Sam helps her figure out a way to minimise the side effects. So she has all the Doctor's knowledge and helps the boys by designing gadgets they can use while hunting. I *think* she is paired with Dean. Any ideas? Thanks.



ETA: Found! It's an untitled fic by dsudis, which can be found here. Thank you julorean!