Even though he just has a passion to help everyone, no matter if human or animal to get healthy again, his favorite jobs was when it were things that help people on a psychological way too. Be it giving back a person with severe burns skin they feel happy with again. A tumor that makes the persons daily live a task. Be it a pianist who got his fingers injured and now needs a good doctor to fix them.
Not only the bodily health of people was important to him, it was the psychological health as well. He is a friendly guy who smiles a lot and likes to brighten up the moods with jokes or optimistic thoughts. This brought him his nickname.
After an accident, which he believes was a failed assassination he can't see colors anymore. His life now is only filled with different grades of grey. He tried his best to hide it from his fellow doctors, not wanting to have to resign. But knowing that it could be dangerous for his patients, he resigned, taking his secret with him.
Following his second passion - Art - and loving to do detailed things with his hand he chose an interesting new profession: Tattoo artists. Specialising in black/white. Something he liked very much and found that even there he could help people in ways he hadn't thought of. Scars that needed a cover up, pictures that helped the people mentally come to peace. And it gave him peace as well.
Not having to look all proper anymore and wanting to keep himself from the urge to cut his own head open to try to fix his problem, and preventing people from asking what the scar is from, he covered his head, back and arms with tattoos. He chose flowers that had medical use and his favorite painting Van gogh's - starry night.
Still, there was this urge to fix himself, to get to see the blue sky again. To see colors of the flowers that now covered his body. So when he got offered a job by a woman who said that they would fund him, his research and would offer a machine that would be a great help with that. He couldn't do anything other than agree. Even though he wondered how she knew.
The Engineer and him got friends pretty fast, using the time they had to travel to their new base thinking up all kind of things. He quickly finds out whats wrong with the doc and both agreed that it might be better if he keeps it a secret from the rest. Just to be sure. They work together so it stays a secret as long as possible.