I don't remember who had this idea but it was a great one - use the figure of Toby from "The impossible planet". This is what he originally looked like:
I had to remove all the signs in his face and on his hands. There are unpossessed Toby figures, but they are hard to come by and more expensive.
Then I used some Milliput to change the sleeves into lab coat sleeves:
Then came the most fun part: I painted the picture on his t-shirt. Might have been easier to just print and glue it, but I was up for the challenge, and I think it looks quite good! For your next Trivia Pursuit, the picture is from the episode "Something Borrowed" where I could get some great screenshots.
Finally I added the coat, which originally belonged to Doctor Constantine from the episode "The empty Child":