Six pirates and six women came from our world to the unpeopled land of Telmar and founded the race of the Telmarines. As Aslan says in "Prince Caspian", they accidentally found in a cave "one of the chinks or chasms between that world and this", and he adds, "There were many chinks or chasms between worlds in old times, but they have grown rarer. This was one of the last: I do not say "the" last." So quite possibly others came to Narnia from our world as well, but Lewis did not record their histories for us.