“So if you’re not Hermann… Who are you?”
”Owen Harper. Who the fuck are you?”
After being accidentally left behind in 2007 Cardiff by the Doctor, Doctor Newton Geiszler finds himself hopelessly lost in the wrong timeline. He is approached by one Capt. Jack Harkness and eventually becomes a member of the Torchwood team as their resident alien biology specialist because of his experience with kaiju in his timeline.
There, he meets and [eventually] befriends Doctor Owen Harper - though he still sometimes refers to his new, slightly cooler lab partner as ‘Herm’ or ‘Hermann’, to which of course Owen snaps at him for constantly.
Their teammates have to remind them frequently that it isn’t a buddy cop movie.