That person, was me. Yes, you read correctly. I met myself.
Donna and I returned to Earth because Donna decided she wanted a McDonalds, so I dropped her off outside, and decided to have a look around the town.
Boarding a train, which has become my new favourite means of travel, I met myself, in a space suit.
I had a rather good conversation with myself. It seemed I (the other me) was on a mission to save Donna from some particularly evil looking mutants who wanted her red hair for their immaculate collection of red hair museum.
Deciding it was best to let myself get on with it, I went back to McDonalds to meet Donna, and we travelled through Time and Space once more.
I decided not to mention my day to her.
All in a days work